I gave the following presentation at the 4th Dijon Money conference (December 10-12 2009):
Steve Keen's Debtwatch Podcast with Stuart Cameron
Briefly, my paper explained how various conundrums that have stymied the development of Circuit Theory for 20 years were in fact the result of confusing a stock (an initial loan) with a flow (the economic transactions that loan could initiate over a year). With a proper dynamic approach, using the “tabular” method that I outlined here in “The Roving Cavaliers of Credit“, the conundrums are easily solved–watch the presentation to see how (click here for my Powerpoint presentation, and the two Vissim files that I ran are linked here and here (you will need to “right click” to download them, otherwise you’ll just get a text file). If you don’t have the free Vissim Viewer, it is downloadable from here. This is one of the Mathcad files that I showed (use a right-click for this one too; it’s poorly structured–written for my use rather than public consumption–but if you have Mathcadyou’ll be able to follow your way around it).
I presented in a parallel session, the morning after the conference dinner, and had a predictably small audience. However that disadvantage had a fortunate side, because that tiny audience included the two conference organisers Louis-Philippe Rochonand Claude Gnos, as well as Basil Moore and Allin Cottrell. Basil is the venerable father of the proposition that the money supply is endogenously determined, rather than set exogenously by the Central Bank, as is still taught (in wild conflict with both the empirical data and actual Central Bank knowledge and practice) in almost all macroeconomics courses; Louis-Philippe and Claude are well-known and respected Post Keynesian monetary economists; Allin is a very capable exponent of Marxian economics, who unlike most Marxists uses computer modelling extensively in his analysis (I just wish he’d update his webpage, which doesn’t appear to have changed since 1997!).
The discussion was therefore possibly better than it would have been, had I presented in a plenary:
Steve Keen's Debtwatch Podcast with Stuart Cameron
However though I was pleased with the way my paper was received by those present, I was very disappointed with most of the presentations at the conference. Though there were some notable exceptions–one of which I’ll comment on below–the papers were either non-analytic (“What Keynes said was…”, “Economists must take uncertainty seriously…”), bombastic (“The fatal flaw in the capitalist system is …”), or used graphical analytic methods that could not easily be distinguished from the content of an ordinary macroeconomic textbook. There were one or two block diagram expositions, but they too were graphical only–mere drawings, not influence diagrams, and certainly not systems dynamics models.
There are many leading Post Keynesians who weren’t at this conference–including quite a few who attended the Australian Society of Heterodox Economists conference that Peter Kriesler organises at much the same time every year–so I’m not claiming that the papers here are utterly representative of the general state of Post Keynesian economics today. Nevertheless, if they were even mildly representative of the work that Post Keynesian economists are doing in the midst of the biggest crisis that capitalism has faced in seventy years–and one which is causing a crisis in neoclassical economics as well–then they will fail to shift economic theory at all. After ten or fifteen years of economic pain, the neoclassical orthodoxy will be reassembled–since it will be true that “there is no alternative”–and Post Keynesians will remain a noisy and largely ignored minority.
Papers like these, though they are intended to criticise the unreality of neoclassical economics, or to point out issues (uncertainty, bounded rationality, open systems, non-ergodicity, whatever) that should be taken seriously in economics, actually strengthen the resolve of neoclassical economists to do nothing of the sort, since they lack any coherent alternative analytic approach.
Neoclassicals who attend such presentations–which almost always include disparaging remarks about the absurd assumptions neoclassical economists make–walk away quite justifiably thinking that “if that’s the best you can do with realism, then I’ll stick to my ‘absurd assumptions’!”
We can and must do better than that. But to do so, non-orthodox economists have to find tools that can express their vision of the economy analytically, either as mathematical or computer models. If we don’t, then whatever might be said by “Critical Realists” about the inappropriateness of mathematical analysis in economics, or how one can’t model open systems mathematically, the critics will be sidelined in a not too distant future by those who do use such models–and who care a good deal less about realism than the critics do. Yet again, the critics may win the philosophical battle, only to lose the methodological war.
That’s why I’ve put in the effort to learn the methods of dynamical analysis in mathematics (systems of differential equations), engineering (systems dynamics), and computing (multi-agent models), and it’s why I’m trying to develop alternatives to those which make sense in the context of economic modelling–notably my tabular method to develop systems models.
These dynamic models enable us to put our thought processes into a systematic framework, and to explore relations that are simply too complex to follow verbally. This is a major benefit to mathematical analysis that is lost in the critiques non-orthodox economists tend to make of how neoclassicals abuse mathematics: when we outline a causal mechanism verbally, we are in fact stating a differential equation verbally. If we say that “Factor X causes changes in variable Y”, we are actually saying “the rate of change of Y is a function of (amongst other things) Factor X”. In mathematical notation, this is d/dt (Y) = F(X).
The advantage of expressing these concepts mathematically, as well as verbally, is that the mathematical rendition keeps track of all the feedbacks and complex interactions that simply overwhelm our capacity to follow a complex causal process verbally, and they give us a means to provide a rough quantification of how strong those feedback effects are.
The failure to do this within Circuit Theory is why a simple confusion of stocks with flows–mistaking the stock of money for the flows that are initiated by a given stock of money over a year–has stymied for twenty years the development of Graziani’s brilliant insights into a workable theory. As I show in the talk above, the simple expression of the flows initiated by a loan are sufficient to solve all the “conundrums” of Circuit Theory. The conundrums were simply the product of applying the wrong type of analysis–simultaneous equations, “period analysis” with its implicit difference equation form, or worse still mere words–to the issue. A simple application of flow analysis in continuous time shows up all those conundrums for what they really are: confusions resulting from bad analysis and inappropriate analytic methods.
Now I also have to exhort my fellow Post Keynesians to learn at least some of the appropriate methods. Get out of the comfort zone of verbal exposition, historiography, simultaneous equations and graphical analysis–and even the much more sophisticated stock-flow consistent framework of Godley and Lavoie (While this method is certainly a major step in the right direction, using it to try to explain where profit comes from was rather like trying to understand how a horse runs, using photographs of a running horse taken at one hour intervals)–and learn differential equations, or systems dynamics, or computer programming. It’s hard, but the effort is worth it. And if you don’t do it, then prepare to once again be dominated by neoclassical economists once the Global Financial Crisis has passed.
I’ll end on one very positive note: there was one exceptional piece of work done by a PhD student (who is also a full-time school teacher) Pascal Seppecher. He has developed a multi-agent model in Java that also simulates the monetary circuit, and reaches much the same result as I do from a differential equations perspective. His model is called Jamel: Java Agent-based MacroEconomic Laboratory. It’s a brilliant piece of work and I do recommend exploring it.
If a full-time school-teacher with a family can nonetheless acquire the skills and find the time needed to do quality work like this, then it’s high time academic Post Keynesians did the same. Sticking with what you are used to, when what you are used to merely lets you point out what “should be” done rather than actually doing it, is no longer good enough.






December 16th, 2009 at 2:04 pm
Hi Steve,
Has the Minsky model been replicated in any other languages maybe like c++. Reason I ask is because if you use more basic languages without the bells and whistles you can probably achieve more in terms of analytical complexity given limited computing power.
December 16th, 2009 at 4:00 pm
GDP came it at 0.2% for the September quarter. Economists expected GDP to come in at 0.4%. These neo-classics just can’t get anything right.
Government borrows tens of billions of dollars and throws it at the economy and all we get is a misely 0.2% GDP for the September quarter.
I thought everything is booming when I listen to Glen (I’m looking confused) Stephens from the Reserve Bank.
December 16th, 2009 at 4:15 pm
I think Glen (I’m confused) Stephens should join his predecessor Bernie (I’m really confused) Fraser and help him flog super on television to the soundtrack of Monty Pythons Flying Circus.
December 16th, 2009 at 4:23 pm
mfo,
if only those neo-classics knew that all those assumptions are ridicoulus they would know that net exports would contribute -1.5% not -1.3% to the GDP outcome, I mean that was so obvious unless you are a stupid economist making stupid assumptions. When will they learn?
December 16th, 2009 at 4:28 pm
Hi Steve,
As alays good points. In fact, so good I’m stuck as to what to say next.
So I’ll try again tomorrow
.
December 16th, 2009 at 4:48 pm
Not yet TININT, though some students have apparently replicated it in Matlab, which can generate C++. And it wouldn’t help all that much with parameter fitting–the main issue is that the number of dimensions scales to the power of the number of parameters. Parallelism is the only strategy to get around that, and even then the algorithms have to be “satisficing” rather than optimising.
December 16th, 2009 at 4:57 pm
@TTNT: 1
Limited computing power!?! Look, I’m a huge fan of C/C++ and use them all of the time. Are you trying to run this on your iPhone? A modern multicore Intel/AMD PC system should be more than able to handle anything which the Circuit model requires. If not, then I would question the programming, and not the language.
That includes Java, which is a relatively large resource pig. Don’t get me started on C#.
The reason why one should use C/C++ is for portability, and being able to run it on more diverse systems. Some of us don’t and won’t use Windows.
December 16th, 2009 at 5:24 pm
Steve,
I enjoyed Seppecher’s simulations, especially the Ponzi shock one. I looked at his paper
(I don’t read French) and saw a bunch of block diagrams but no definable equation system to run on a spreadsheet.
I’m hoping you will modify your basic model to accommodate a Ponzi bubble – maybe a productive sector and a real estate sector. I hope the Great Depression isn’t over before your model achieves immediate relevance.
I wish you would pitch the MathCad in the rubbish and present your system on a computer spreadsheet. I’m afraid those who are half interested in your model don’t want
to go buy some silly math program. What would Keynes do?
December 16th, 2009 at 6:37 pm
Steve, Your important point in the presentation – true dynamic analysis is required to specify the system’s elements correctly and then demonstrate/compute the results – came through loud and clear. Congratulations.
Keynes argued that math was not the basis of method in economics because economics is a system of logic. Your demonstration of Mathcad, with its auto generation of the diffential equations, caused me to wonder if technological advances (i.e. computers and math softwares) might have Keynes ammending his position on math. Perhaps to something along the lines of agreeing that an iterative process of logical specification, testing in dynamic analysis, and re-specifying the logic is now the order of the day for doing economics.
December 16th, 2009 at 9:45 pm
[...] This post was mentioned on Twitter by Vaidyanathan – India, Danny Yee. Danny Yee said: post-Keynesian economists need to use better mathematics http://tinyurl.com/yejsnp4 (DebtDeflation) [...]
December 17th, 2009 at 2:05 am
Warren Raftshol
I do not know of a spread sheet that can do differential equations but understand your problem.
There is however an open source program which was recommended to me by Steve Keen. It is called “scilab” and Steve’s code can be translated to run on this program. There is also a companion open source, graphical input program called “scicos”. Just google these names to find where you can get a free download.
cheers
December 17th, 2009 at 2:55 am
Thanks BrightSpark1 for the info, but I was trying to make the point that Steve’s
equation systems are so simple (first order linear) that anyone with a spreadsheet
can set them up and, merely by taking small enough time steps, can get the same
results as the MathCad program. To my way of thinking, that would make his method
more accessible to a wider audience.
But I will check out your suggestions.
December 17th, 2009 at 5:37 am
It’s not the model itself Eternal Student, but parameter fitting it to real data.
The basic model I’ve shown is a cinch in that regard–a mere 8 equations and only a couple of structural nonlinearities (dividing one variable [F_D] by another [Wage W] to derive a third [L Labour], that sort of thing. But the multisectoral model I’ve developed has 40 ODEs, 5 nonlinear behavioural functions and numerous structural nonlinearities. That would take a supercomputer to do an adequate parameter fit, C++ or no C++. And you’re right, the main appeal is portability.
December 17th, 2009 at 5:41 am
Keynes would learn to use something more sophisticated than a spreadsheet Warren, if the need was there! Sorry mate, as you know I’m impressed by your spreadsheet implementation of my model, but when you get beyond the single sectoral stuff a purpose built Math program–whether Mathcad or anything else–is essential (even if that means Fortran for instance).
A better approach is to implement my system in a free package like Scilab. Then you’d be “cooking with gas”. For me, already knowing how to use a program with a very straightforward user interface matters, because I’m still at the developmental stage and I don’t want to be struggling with the GUI (or absence of one!) in a more freely available program just yet.
December 17th, 2009 at 5:42 am
I would hope so Chuck! One of Keynes’s most famous aphorisms was “When the facts change, I change my mind. What do you do?”. I would like to believe that he’d be designing an iterative “verbal concept–ODE implementation–check of behaviour–amend verbal concept” approach, with tools like this now available.
December 17th, 2009 at 6:45 am
@Steve 13:
Perhaps I’m mistaken, but from your description it sounds like it’s one of the Embarrassingly Parallel type of problems. Is that correct?
December 17th, 2009 at 6:57 am
“For every complex problem, there is a simple solution….and it is nearly always wrong.” H.L.Mencken
Dynamic models help us understand complex issues. They can often have hidden benefits – if you need to constrain the model, or if the model crashes, there can be an analogy in real life. In biology, this is death, in finance a crash or panic.
December 17th, 2009 at 7:02 am
Yup. Any nonlinear model is when of sufficient complexity. Unlike a linear model where there is only one “basin of attraction” if the equilibrium is stable, a nonlinear has many such basins and the equilibrium doesn’t necessarily describe the system location anyway–I have to reproduce cyclical data so it’s then the case of which parameters best approximate the cycle given my model and the data. With 40 ODEs and so many parameters, the search space is effectively infinite so you have to use search algorithms over a strongly partitioned parameter space.
I’ve known about this for decades but this will be my first attempt to actually apply the knowledge. I will be in the backroom for quite some time working out how to do it.
December 17th, 2009 at 8:39 am
Hi Steve,
Long time lurker and reader (several years now…) Speaking of supercomputers I was attending a conference, ComBio 2009 in Christchurch NZ, last week and was reminded of your modelling. I came across a NZ research group called Blue Fern based at the University of Canterbury. Who have up and running two IBM supercomputers: an IBM Blue Gene and an IBM p575 super cluster. I was having a chat and they are quite keen on developing relationships/collaborations with just about anyone who can put their systems to use. Are you aware of them?
They have been doing some economic modelling on CDO’s with a NZ based economist. Through my own research I have been involved in a few NHMRC international linkage grants with Canterbury (in the fields of bio/organic chemistry) over the years…not sure but I would presume ARC has a similar international linkage scheme running.
Might be an option if you require some serious number crunching with only a small flight across the ditch…
Cheers
December 17th, 2009 at 9:39 am
WOW
http://www.time.com/time/specials/packages/0,28757,1946375,00.html
December 17th, 2009 at 10:18 am
Steve,
I haven’t seen your latest model but as far as I know the issue may not be as simple as just extracting parameters from the real data.
I understand why you are using Mathcad and Vissim but I believe this is not the way to sell your models. Unfortunately not too many people will be interested in jumping through all the hoops to install a demo version. I am not in a dire need to steal Mathcad even if there are cracked versions floating around the darker side of the net. So I have to wait for something readable.
Unfortunately it looks that it’s you who wants to convince other economists to your models (not the other way around) so the burden of proof that they are correct is on your side. For me it is good enough if you just write the diff. equ. matrix in the symbolic form and define parameters with starting values – then I can type them into scilab.
A few articles already contain what is needed to reproduce the simple model and some people have done it. I am waiting for the full model to be published even if it is just a skeleton.
I am still slowly digesting earlier models and I can see a few potential issues. I see no point in fiddling with the parameters as long as I am not fully convinced that the principles of the model are closed to the reality. Otherwise we will have another go at the Marsian economy (or rather Marxian – what’s the difference?)
If what I have written in this post only shows my ignorance – please forgive me and gently nudge me to the right path.
Building a model to prove that the credit money circuit can work (a proof of concept) is one issue – this task has been completed and this is a real achievement.
But even getting close to the point where current TRYM is (can be used for short-term predictions despite the fact that the model topology is incorrect – because short-term response is based on the empirical data) may be difficult or impossible if certain fundamental issues are not addressed.
For example is it right to clump together firms with a different money turnover (production and sales) period? I will not use the term “time lag” as it is ambiguous.
How a variable money turnover period affects the dynamic behaviour of the system during a recession? It is well known that companies cannot sell their products and get money back in time.
When we look at the Marxian M to M+ production model – will it still work when there is inflation? That is you buy 1000kg of raw material for $1000 at the point of time you spend M but when M+ is extracted – you would only buy 900kg of the raw material – the same applies to the value of product. Is it beneficial for the producers to effectively speculate on the commodities used in the production process?
What happens to the M to M+ process when we have deflation?
Have you included capital goods in the latest version of the model – the value of long-term investment in the means of production?
Shouldn’t we include financial and non-financial assets in the model? What about the “production” of houses and gold? What about Treasury bonds (and “bond vigilantes”)? Do they fit into the next-generation model?
Finally we have to determine based on empirical data whether we more live in a fiat money world (Chartalist-like) or in a credit money world (Circuitist-like). What if the world is Circuitist in regards to investment and assets in general but it is more Chartalist-like when it comes to production and spending? From what I know there are rather successful firms which do not rely on credit at all – all the working capital has been grown organically from the initial investment. This is more likely in countries which experienced a period of disinflation.
What about the government, taxation and direct spending? Can we include these 20% of the grey sector economy when we model Greece or Italy? If we fret about the 2% drop in GDP we have to include this as well:
http://www.economist.com/businessfinance/economicsfocus/displaystory.cfm?story_id=2766310
What about introducing hard limits on the consumer demand? How many cars can I fit into my front yard?
Production cannot grow forever. What about hard limits of the availability of commodities? Can we start extracting oil at the twice the current rate? I doubt it – it would be too expensive.
I am asking all these questions because it may be very easy to assume that if we can see a cyclical response of the system – we have cracked how the economy actually works. But the most of the systems described by the type of differential equations you are using either display an oscillatory behaviour or are unstable. If the model is not reflecting the reality but looks nice – the temptation to draw far reaching conclusions (“a collapse is looming”) may be too strong and another trip to Mt Kosciusko is inevitable.
Anyway I listened to the discussion on the podcast and these nice guys who were there might be brilliant intellectuals but they wouldn’t be hired by any commercial enterprise. Neoclassical economists are sometimes hired – even if the talk rubbish, their models have been patched so many times that in fact they can predict the short-time outcome.
Your methodology is far more advanced. I hope that a real working simulation of the economy (at the macro scale) based on differential equations is a few months or years away and you’ll get it right.
December 17th, 2009 at 10:21 am
bb,
He only won because Tiger left the competition and went into hiding.
December 17th, 2009 at 10:47 am
… also if we know that the model topology is right we may attempt to extract its parameters from the real data (this is difficult for a dynamic model as constructing an error function is problematic and then the iterative process of minimising error function will most likely go to nowhere due to the presence of the local minima and the butterfly effect – we have a dynamic system not a static one).
But the right approach is to get the parameters a-priori (like production-sales cycle time period for an industry), put them to the model which then should just work and run closely to the reality. This is almost the ultimate verification of the hypothesis (but not a formal proof).
TRYM may be a set of 2-nd order dampened oscillators but at least they might have got the coefficients right so the short-time response may reflect the reality. But TRYM’s predictions time horizon is until the next elections I presume so they can afford to ignore anything else.
Anyway it’s time to start the more boring half of the day.
December 17th, 2009 at 12:30 pm
Graziani’s 1989 paper is impossible to get hold of. anybody knows about an online version of it somewhere?
December 17th, 2009 at 12:57 pm
@Steve 18:
I’m glad to hear that it’s an Embarrassingly Parallel type of problem. Which means that Distributed Computing can be applied to it. And which is (I suspect) why you’re interested in cross-platform portability. All of which is what I do professionally.
At least on the UNIX/Linux side. I don’t do Windows. Let me know if I can help.
December 17th, 2009 at 1:28 pm
Eternal Student,
Extracting parameters of the model from the empirical data requires non-linear optimisation. In my opinion this may be even impossible in the case Steve is talking about as the error function must be convex within the range of parameters the solution is sought. (There are some methods bypassing this constraint but they may not work).
How to define the error function is another issue (which metrics to use?)
It is possible to run some type of distributed error function minimum search algorithm but I believe that much more fundamental issues must be addressed first.
BTW what about writing a distributed simulation with clustering agents and disributing them across several hardware nodes? Imagine you have a collection of objects (persons and firms) which synchronously run an iterative process (work/buy/sell etc) and at the end of every iteration fire messages to other agents. Then a routing component may be added and these messages which are to be delivered to a remote agent would go through a socket. This can be scaled horizontally to multiple hardware nodes (processes running on multiple processors). It may be possible to generate a population of millions of agents.
Would you like to have a go? Has anybody implemented anything like that?
December 17th, 2009 at 1:42 pm
You got it in one ES. I’ll be in touch!
December 17th, 2009 at 1:45 pm
Hi Steve,
Since you use lots of software to devlop your models, what do you think of many fund sites “online tools” to track different markets?
December 17th, 2009 at 2:22 pm
Nudge, nudge: Still nothing showing up on the Debitwatch RSS feed.
Wonder how long it will be before debtdeflation.com ends up on the government interwebnet blacklist…
December 17th, 2009 at 2:40 pm
Strange; I’l check with Steven Richards and see what might be going wrong.
December 17th, 2009 at 3:45 pm
Chuck Willer
December 16th, 2009 at 6:37 pm
“…Keynes argued that math was not the basis of method in economics because economics is a system of logic. Your demonstration of Mathcad, with its auto generation of the diffential equations, caused me to wonder if technological advances (i.e. computers and math softwares) might have Keynes ammending his position on math. Perhaps to something along the lines of agreeing that an iterative process of logical specification, testing in dynamic analysis, and re-specifying the logic is now the order of the day for doing economics.”
Here is a good blog on math and answered that very question of logic and math:
http://scienceblogs.com/goodmath/2009/12/what_is_math.php
An open source math program:
http://www.sagemath.org/
which uses:
http://www.python.org/
also see:
http://www.scipy.org/
http://numpy.scipy.org/
December 17th, 2009 at 3:53 pm
Hello Steve
Your 18 regarding “basins of attraction” have you considered the simulated annealing technique to determine probable outcomes?
You must be turning on some lights in some dim neoclassical brains, that session was very well done.
December 17th, 2009 at 4:01 pm
I have a bit of experience calibrating models to market data mainly for option pricing but some of the knowledge is probably portable. Some of the models include stochastic volatility and HJM, both really difficult to calibrate.
When I look at the Minsky model in terms of calibration I would imagine you would need a pretty big error tolerance to obtain any solution. The reason for this is because I imagine that some of the parameters actually exhibit some random behaviour. I think the proper way of doing it would be first to somehow filter out the noise out the data.
Alternatively you could actually introduce some stochastic terms into the model to absorb some of the noise. At most from my experience you would be limited to 2, or 3 if you are ambitious.
December 17th, 2009 at 6:54 pm
@ak 26:
Distributed Computing across several nodes is old hat. Check out Beowulf technology for starters. It came out in the 1990’s. Cluster computing is used by so many people, companies and research groups that it’s a serious business.
There are different approaches; it really depends on what you need to do. And the pitfalls are many, especially if you want to scale to the magnitude that you’re talking about.
So, yes, it may well be doable. But I’d really have to take a look at the software that we’re talking about, and what exactly needs doing.
What’s the best way to get started on Linux? I had thought someone mentioned some Open Source package which would run Steve’s Circuit model, but I can’t find the reference. Anyone know? TIA.
December 17th, 2009 at 7:12 pm
It’s Scilab ES: http://www.scilab.org. There are several others as well I’m sure (Arthur Dent noted a few). Anything with ODE solving capability, and preferably also a symbolic engine.
December 17th, 2009 at 7:13 pm
It’s one of many possibilities BrightSpark–others include the Levenberg-Marquardt algorithm, which is the first I’ll try. GAs, etc…. lots of options.
And there were no neoclassicals in that audience–I was trying instead to motivate lazy Post Keynesian brains!
December 17th, 2009 at 7:35 pm
Eternal Student,
Scilab can run these models and you can run multiple instances of simulation on multiple nodes at the same time just write a small application or script populating parameters, kicking off the simulation and harvesting data from the nodes afterwards. We’ve done something similar in perl for harvesting performance measurements for the previous company.
This is scilab:
http://www.scilab.org/
I can convert a model into the scilab format. If you want to do it on your own it I can send you a link to a simple manual when I’m back home and you’ll only need to waste about an hour to learn how to do it.
I haven’t timed scilab. I am assuming it is quite fast. If not in the end somebody can write Runge-Kutta in C
http://www.physicsforums.com/archive/index.php/t-1448.html
and create a distributed application doing error function optimisation or whatever calculations you want (don’t know maybe a genetic algorithm search for the parameters).
An alternative is to use Matlab (can be integrated with the C++ code) but it is expensive.
So I recommend scilab and a simple scriping-based solution.
The only issue is that I don’t believe this approach of parameters extraction will work for so many parameters and an error function which may not be concave. Maybe a kind of semi-random search combined with a genetic algorithm may do – but this is not trivial on its own.
I played with the non-linear programming briefly about 16 years ago.
Steve needs to clearly specify what he wants to achieve. If the problem is well defined I would be very happy to contribute.
Let’s leave the distributed agent system for another discussion.
December 17th, 2009 at 9:04 pm
Ok I have been thinking about this.
In my previous post I mentioned adding stochastic terms. Not that any cares I don’t think this is appropriate, details why are a bit fuzzy in my head but in some state of thought I was convinced that it’s not.
The optimisation seems to be to find a set of fixed parameters presumably the constants in the ODE’s such that you get some fit to published market data. OK – this is not possible, in my opinion, clearly you could never really prove that it is impossible to do something.
So why is that not possible? In my opinion, yes the model is good and captures some reality in terms of dynamics, but in terms of parameters I think they are not constant, in reality.
But I have an idea and I think it may have some potential.
If the parameters are not constant then take the next step, make them discrete functions in time. Take your nodes at some arbitrary interval say 1 month, or to coincide with your data which has some period. Then calibration becomes very easy because you just have to calibrate at each discrete interval for the discrete parameter values for that interval.
This could have many potential outcomes. First you may show that the parameters do in fact change. This in itself would be a discovery. Second you would actually have a model which is closely calibrated to historical data. Third you could actually then study those parameters and may get further insight from their behaviour, they may be cyclical, may be they follow some AR process, point is it would provide a lot of data where if some relation could be found would also be a good discovery.
A dynamic model with time dependant parameter set would fit in with my intuition of the economy.
December 17th, 2009 at 9:16 pm
ak,
“Steve needs to clearly specify what he wants to achieve. If the problem is well defined I would be very happy to contribute.”
sorry I have to say this, I hope you take it with some sense of humour. you are absolutely correct but this is very typical IT talk! This is why BAs earn so much money writing crappy specs and business requirements…
Maybe with our collective expierence we could help to also specify the problem.
December 17th, 2009 at 10:34 pm
This is the scilab ODE manual:
http://www.math.univ-metz.fr/~sallet/ODE_Scilab.pdf
December 17th, 2009 at 10:52 pm
Good morning Prof. Steve Keen,
I’d wish to thank you for your efforts, I’m a new comer here, and have a lot of questions for a long time, since the .com bust, which I trying to find answer for myself, and your site is one of rare sources of scientific information on economy… I’ve bought your book “Debunking Economics”, which should arrive shortly. I hope, I will find some of the answers. In mean time, reading the articles on this site, I’ve an impression, that the result of your work points to inevitable collapse of deb-based economy, which has begun about 2 years ago. And for which there is no solution, for exceptions for very drastic ones, such as planetary Jubilee, which, I’m afraid, could result in another world war. For this reason I’m interested in alternative economic systems, which could help to avoid the disaster. One source of information on this subject, which I’ve found very interesting is post-marxist theory developed by ‘Predictor’ group in Russia, I’m very interested to hear the your opinion on their ideas, the manifesto could be found here: http://dotu.ru/2002/08/12/20020812-macroeconomy/
It is pretty brief, but touches a very broad specter of world issues.
Can you recommend some reading on this subject?
Thank you very much in advance, and excuse me for my English.
A. Romanov
December 17th, 2009 at 11:34 pm
“..Basil is the venerable father of the proposition that the money supply is endogenously determined, rather than set exogenously by the Central Bank, as is still taught (in wild conflict with both the empirical data and actual Central Bank knowledge and practice) in almost all macroeconomics courses;”
I’m very unintellectual person, but just a thought: Does this has something to with Russell’s paradox?
http://en.wikipedia.org/wiki/Russell_paradox
December 18th, 2009 at 12:31 am
Two questions: 1) Is there a “conundrum” still when debt is repaid? What happens?
2) Looking at your last chart it appears that QE does not pose much of a problem for inflation, but that fiscal stimulus is a serious inflationary problem. Am I looking at the charts correctly?
December 18th, 2009 at 4:05 am
1st post by a non-economist (industrial engineer) so be gentle.
It might be well known here as you talk about “systems dynamics” but are you familiar with the work of J Forrester at MIT on “systems dynamics”? If you use Vensim then I guess you might be.
There have already been popular articles linking his work and the non-linear nature of the crisis. http://simgua.com/documents/SB_Forrester.pdf
He was a pioneer in taking dynamic stock-flow modelling from control engineering and applying it to social systems (initially industrial supply chains).
His last project before he dies is a book and model on “a general theory of economic behavior”. It isn’t clear when (if!) it will be finished.
Here is a conference paper about it from 2003 which includes a brief critique of neo-classical economics:
http://sdg.scripts.mit.edu/docs/D-4886-2.JWF.EconTheory.pdf
This model has been in development for “several decades” and includes over 1000 equations.
I don’t know how useful all this is, I can add more thoughts if you think they would be relevant… I’m an interested observer in both systems dynamics and economics. I was quite scared when I realised the analytical ignorance of mainstream economics by reading this paper http://mises.org/journals/qjae/pdf/qjae7_1_10.pdf . That and the crash sparked my interest!
More info on Forrester/ Systems Dynamics here: http://www.systemdynamics.org/JWForresterBio.pdf
Final point: if you are looking at modeling software that is free/easy to access http://www.sagemath.org might be an option. Its interface is through the Firefox browser. You can install the software yourself or use it over the internet from a remote server. It has an interface with Scios.
Conal
December 18th, 2009 at 8:06 am
We’d actually be rougher with an economist who signed on Conal–quite a few members here are engineers. I doubt that there are quite as many economists aboard.
Yes I am familiar with Forrester, and one of my closest colleagues in the nonorthodox economics tradition is Mike Radzicki, a graduate of Forrester’s program at MIT and a past-President of the Systems Dynamics Society.
However I tend to take a more direct mathematics approach to my modelling–reflecting my training and preference for working directly in ODEs rather than block diagrams–and I have stronger links with the systems engineering approach which diverged from systems dynamics a few decades ago. There is no real difference between the two groups in philosophy, but their modelling approaches are different as are their tools: Vensim for the SD crowd, Simulink for the SE lot. I’m a bit eccentric there too and prefer Vissim.
Thanks for that link to the Austrian journal paper, it was excellent. And yes, it’s bizarre that dimensional analysis isn’t practised in economics, but that’s a side-effect of the analysis being equilibrium-oriented to begin with: they don’t even learn dynamics as undergraduates (99.9% of them anyway) and aren’t even aware of the issue, as that paper points out.
When I have something vaguely resembling spare time, I will have a play with Sage–Arthur Dent here has also recommended it.
December 18th, 2009 at 8:07 am
That’s giving neoclassical economists too much credit kjr63: it’s simply ignorance on their part and the fact that endogenous money undermines some core beliefs (such as money neutrality) which they preferred to realism.
December 18th, 2009 at 8:10 am
Your English is far superior to my Russian aromanov! -:)
I had a quick scan through the manifesto, and I can’t say that I was particularly persuaded. I think this may reflect Russia’s own tortured history with social experimentation, more than a model for effective social change; and it doesn’t appear particularly portable outside Russia.
On economic reform in general, I would call myself an Evolutionary rather than a Revolutionary, and I am more interested in small changes that have profound effects than in attempting a profound change that may have unintended effects–as was the case with Socialism itself.
December 18th, 2009 at 8:17 am
Not too impressed with the mathematical logic generally–Gaussian error bounds, etc.–but the graphics are often swish and the data is to die for. Wish I could afford a Bloomberg subscription…
December 18th, 2009 at 12:19 pm
ak and steve:
Thanks, gents. I’ll start taking a look at scilab shortly. Sorry for the delay in responding here, but I came down with a Winter cold today.Nothing major, and I’m starting to feel better already.
ak – You are absolutely right about having well defined goals. This is especially important with complex projects.
Myself, I need to know what I’m dealing with before I can make any commitments.
December 18th, 2009 at 3:35 pm
This is part of the reason why the slowdown has beed mild in Australia. Australia benefits from Chinas ‘domestic consumpion’. The Chinese like to collect vacant, zero rent, zero yield, housing and commercial building assets as a ’store of value’
http://www.youtube.com/watch?v=0h7V3Twb-Qk