The cobweb theorem is an economic model used to explain how small economic shocks can become amplified by the behaviour of producers. The amplification is, essentially, the result of information failure, where producers base their current output on the average price they obtain in the market during the previous year. This is, to some extent, a non-rational decision, given that a supply side shock between planting and harvesting (such as an unexpectedly good or bad harvest) can lead to an unexpectedly lower or higher price. This results in either a higher output or a lower output in subsequent years, and moves the market into a long-term disequilibrium position.
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