Explaining the Downfall

Bernanke made some speeches recently about how the housing bubble was caused by bad regulation not because of low interest rates.

However, Forrester disagrees. I still have to find the original posting, though.

However, he also says that this recession along with the Great Depression was just part of the economic long wave, the Kondatrieff Wave. That might imply that there was no cause and that nothing could have been done to prevent it.

This excerpt is from his paper System Dynamics and the Lessons of 35 Years 1991

In a similar way at the national level, the System Dynamics National Model shows that puzzling and controversial economic behavior arises directly from known structure and managerial policies (Forrester, 1979). By building production sectors of the National Model using managerial policies derived from 20 years of corporate modeling, we find that most economic behavior arises from the private sector. Governmental taxation and monetary policies have less effect than usually assumed and lack the expected leverage for controlling economic behavior. The Great Depression of the 1930s has been blamed both on restrictive monetary policy and on protective tariffs, but we find that depressions arise at 45 to 60 year intervals as a result of the economic long wave, or Kondratieff cycle, which is driven primarily by major shifts in private-sector incentives for investing in capital plant, borrowing, and saving (Forrester, 1977; Sterman, 1986).

Debate about the economic long wave illustrates the situation depicted in Figure 3 (Kondratieff, 1984; Freeman, 1983; van Duijn, 1983). There is little acceptance by economists of the idea that structures could exist capable of producing a major economic fluctuation with some 50 years between peaks. Yet much of the theory for such a long economic wave already is established in the mainstream of economic thought.

In teaching macroeconomics, the classic multiplier-accelerator process is often used to explain short-term business cycles having 3 to 10 years between peaks. The multiplier (rising consumer income causing increased demand) and the accelerator (rising demand causing increased capital investment, wages, and consumer income) represent widely accepted and fundamentally correct assumptions about structure and policies belonging in the top category in Figure 3.

However, the belief that the multiplier and accelerator interact to cause short-term business cycles arises from an assumed dynamic solution to the equations describing the structure. The assumed dynamic solution belongs to the middle category in Figure 3 where beliefs are often incorrect.

While investigating cyclic economic behavior, several system dynamics investigators have shown that the multiplier and accelerator are not significant in creating short-term business cycles but are powerful contributors to generating D-4224-4 19
much longer cycles having several decades between peaks (Forrester, 1982,
(Nathan B.); Low, 1980; Mass, 1975).

Even though the economic long wave has been broadly rejected in economics, the accepted multiplier-accelerator relationships go far in explaining long-wave behavior. Here we see a common situation. Both sides in a debate can usually agree on underlying assumptions. But there is disagreement about the dynamic consequences. Building those accepted assumptions into a dynamic model begins to resolve differences arising from incorrect intuitive solutions to complex systems.