State Space Models

All state space models are written and estimated in the R programming language. The models are available here with instructions and R procedures for manipulating the models here here.

Thursday, November 12, 2026

Adam Smith III: What Controls the Economy?

 


The Small Country simulation (above) looks very much like a Random Walk and cannot be identified without estimation (see the System Matrix below). The System Theoretic definition of a Small Country is one that has no State Variables. The difference between a Small Country and a Random Wak model is that the Small Cpuntry models is stable (see below).







Notes



Adam Smith Controller


Adam Smith Small Country System Matrix







Adam Smith II: The Small Country




Neoclassical Economic Growth models seem to be designed to explain growth in large, industrialized countries with large populations, urban labor forces, modern capital stocks and advanced technologies. But, large countries are not the only states in the World System and my question is whether Economic Growth theory adequately explains the development of these countries. The answer is: it doesn't!

We have to go back to the Classical economists to find models that are more appropriate.





Notes



 

Wikipedia Links


Adam Smith Random Walk




Adam Smith Small Country Model





Adam Smith Controller




Sunday, November 8, 2026

Why Bother Developing Simple Causal Models of Economic Systems?


This Page is UNDER CONSTRUCTION.




 

Why Bother Reading the Classics?

  


The Classical Economists, Adam Smith (1723-1790), Thomas Robert Malthus (1766-1834), David Ricardo (1772-1823) and Karl Marx (1818-1883), collectively wrote in the 18th and 19th Centuries. All their works are currently in the public domain and available on line (see below). Neoclassical Economics supposedly made their works obsolete and you hear little about the Classics if you take a course in ECON 101. Still, there is a sinking feeling in the Economics profession that We Need Better Economic Models. What might the Classics have to offer? Briefly:

  • The Steady State Economy Modern economics assumes that growth can continue forever without limit. The Classics, on the other hand assumed that eventually growth would reach a steady state. For Marx, this was the Communist Society, which he described only general terms. There is evidence that current economies (here) are reaching a steady state and that it will not be a utopia.
  • Economic Depressions and Business Cycles In Modern economics, cycles and long-waves are not supposed to happen. The market is supposed to adjust any imbalances in supply and demand and regulate the economy. The Classics assumed that booms, busts, panics, bubbles and manias could all happen and required explanation. For example, Malthus and Ricardo were concerned about effective demand, prefigured Keynes and did not assume markets handled all economic problems automatically.
  • Historical Determinism Modern economics has no role for History. Models are timeless and general, much as universal physical forces. The Classics, particularly Malthus and Marx, understood that different models were required for different periods. Premodern societies are best described by the  Malthusian Stagnation Model rather than the Neoclassical Growth Model. Marx thought that the Asiatic Model of Production was different from the Capitalist Model.
  • Alternative Economic Models can be developed based on the Classics (see below). The models can and should be tested. Right now, the Neoclassical Economic Model is dominant and it is incomplete.

Modern Economics based on overdetermined, stable equation systems doesn't have a role for cycles, depressions, pre-modern models of production and History. Systems Theory, on the other hand, can easily handle cycles, instability, growth and steady states.  Not that every problem is solved by recovering the past. Both the Classics and the Moderns jumped too quickly from their (mental) models to policy recommendations.  Real SocioEconomic systems are far too complicated to be controlled by simple feed forward systems. The best we can do is analyze natural experiments as they are conducted in History and see if our systems models can capture what happened. 

The bigger problem here is that Economics has been co-opted by Neoliberalism and Market Fundamentalism. What you get in ECON 101 is an attempt to describe the Economic System and an attempt to proscribe policy measures to tell politicians how to run the Economy. These attempts are largely a failure and have little historical justification or empirical support--at least the little that is offered in ECON 101. And, this is what the average student gets, if anything, as an introduction to Economics.

The Classical writers had very few mathematical, statistical or historical tools at their command for understanding the Economic System. They struggled with definitional issues and wrote in a verbose style we no longer find very straightforward. If we trained students to be Classical economists, we would just end up generating an avalanche of speculative, qualitative writing that never gets tested. In other words, we wouldn't get Science.

My recommendation is that we use the new tools available to us, primarily Systems Theory, to move on from both the Classical Economists and current Neoclassical Economics. Critics will argue that this has already been tried an failed, in Sociology by Talcott Parsons (1902-1979) and in Economics by Kenneth Boulding (1910-1993). The critics are wrong but having an argument won't solve anything.

Let me just make these assertions: Economics went wrong by insisting that everything has to be derived from individual, rational behavior, i.e., Homo Economicus. Systems theory argues that the the Economy is not just an aggregation of individual, rational behaviors. The system has both aggregate growth and aggregate feedback processes. We understand the variables involved in Growth (the Neoclassical Growth Model) but we have little understanding of the macro-feedback process and how the Economic System is controlled beyond the Aggregate Demand and Supply model (AD-AS model) which is incomplete. Just consider the simple Impact Model with markets for aggregate production (Q), energy (PE), and CO2 (PC, price of carbon--a market which is very incomplete).


What controls Global Temperature (T)? What controls Population Growth (N)? There are other Human Feedback Loops in the complete TechnoSocial system that we barely understand. The Subprime Mortgage Crisis (2007-2010), the COVID-19 Pandemic (2019-2023) and the resulting economic shocks and fumbled government response made clear that markets didn't help control inflation and we really didn't understand the effect of many supply chain delays and disruptions caused by exogenous shocks. And, the expanded Impact Model above is not a system because there are no feedback loops (just self-loops).

In summary, we should continue to be interested in the Classics because they asked the right questions. We have to get beyond the Classics because the tools available to them (arm-chair speculation) did not produce the best answers. Western Civilization has not collapsed (yet). All the -isms (Liberalism, Communism, Fascism, Socialism, etc.) are flawed. And, we have new questions based on Systems Theory: Is the Economy Stable? Is the Economic System Under Control? What feedback loops are activated by crises? So many questions.


Classic References

These works are available on line:

Excellent Secondary Works

These secondary sources are worth tracking down and reading:

Adam Smith I: A Random Walk of the Invisible Hand

 



This Page is UNDER CONSTRUCTION but you can watch the video above and follow the links below until it is completed.


As the graphic below shows, Adam Smith (1723 – 1790) is considered the Father of Classical Economics.


He influenced David Ricardo, Karl Marx, Thomas Robert Malthus, Neoclassical Economics and everything after (Joseph Schumpeter, World-Systems Theory, Limits-to-Growth, Unified Growth Theory, and The DICE Model Dynamic Integrated Climate-Economy model).

The problem with this 250+ year History of Economic Thought is that, while the Sources of Economic Growth have been fully studies and understood, control of the Economic System, Feedback Loops and the Limits-to-Growth have not. Khalid Saeed (2005) went back and analyzed the Classical Economics looking for what writers thought placed Limits on Economic Growth. He found that this strain of Economic Theory had largely been forgotten in the rush to develop a Strategy of Economic Development.

Saeed (2005) developed System Dynamics models for Smith, Malthus, RIcardo, Marx and Schumpeter concentrating on how each thinker saw the Limits-to-Growth. In this post, I will start with the Smith Model, but rather than just replicate Saeed (2005), I will estimate State-Space (SS) and Dynamic Components Models (DCM) from the output of Saeed's (2005) models. The purpose of the exercise is to (1) allow the models to be estimated (see Cole et. al., 1973 for a filed attempt to estimate System Dynamics models) on historical data from any country and any time period and (2) allow us to identify the Control Components for each model.

Saeed (2005) develops two Smith Models, the first with a "Labor "Constraint" and the second without.

Labor Constraint

From a causal diagram of the Smith Model, based on the Kaya Identity (see below):



Since Labor (L) is the only exogenous variable (Technology, T, and  Capital Stock, K, are endogenous and based on Investment), it provides the only constraint on the system.


Without Labor Input, the system goes quickly to equilibrium (Saeed's data above). When estimated the year-to-year model is a Random Walk (RW, see below) and the Attractor Path Model (a free simulation starting at time one) has no state variables and would be recognized as a Small Country Model (see below).

You can inspect actual examples of countries, during particular time periods, that are Random Walks here.


Notes


Kaya Identity

The Kaya Identity is a mathematical identity that disaggregates the total emission level of the greenhouse gas carbon dioxide so that it can be expressed as the product of four calculable factors: human population, GDP per capita, energy intensity (per unit of GDP), and carbon intensity (emissions per unit of energy consumed). It is a concrete form of the more general I = PAT equation relating factors that determine the level of human impact on climate. Although the terms in the Kaya identity would in theory cancel out, it is useful in practice to calculate emissions in terms of more readily available data, namely population, GDP per capita, energy per unit GDP, and emissions per unit energy. It furthermore highlights the elements of the global economy on which one could act to reduce emissions, notably the energy intensity per unit GDP and the emissions per unit energy.


As a causal diagram (above) I use it as the basis for all the theory development. The 
Kaya Identity is true by definition.

State-Space Theoretical Dynamic Component Models

Wikipedia Links


Adam Smith Random Walk