Road Map We begin by looking at some facts about the Great Depression and the boom that preceded it. Our goal is to see if we can develop a good explanation of these facts. The most fundamental defining feature of the Great Depression was the large and sustained decrease in real GDP. In the figure below, which shows the circular flow of income, reminds us that real GDP measures both production and spending. The Circular Flow of Income
GDP measures the production of an economy and total income in an economy. We can use the terms production, income, spending, and GDP interchangeably. It follows that during the Great Depression, both output and spending decreased. Perhaps it is the case that production in the economy declined for some reason, and spending decreased as a consequence. Or perhaps spending declined for some reason, and production decreased as a consequence. We examine two approaches to the Great Depression, based on these ideas. One sees the root cause of the Great Depression as a decline in the productive capabilities of the economy, meaning that firms—for some reason—were unable to produce as much as they had before. This then led to decreased spending. The other approach sees the root cause of the Great Depression as a decline in spending, meaning that households and firms—for some reason—decided that they wanted to purchase fewer goods and services. This then led to decreased production. We look at each explanation in turn. We investigate which inputs contributed the most to the decrease in output and also look at what happened to the different components of spending. This more careful look at the data helps us to evaluate the two competing theories of the Great Depression.