The J Curve is a theory that revolves around the economics of currency depreciation. When a country's currency depreciates, its exports become cheaper and its imports become more expensive. This causes a rise in the demand for the cheap exports and a decrease in the demand for the expensive imports, resulting in an initial worsening of the trade deficit and a worsening of the balance of payments. The goal of the J Curve is to show that the short-term deficit caused by this initial market adjustment will eventuate in a return to a trade surplus – thus the ‘J’-shape that appears on a graph of the trade balance.

The J Curve can be applied to a range of different economic situations. In the medical profession, for instance, it can show how an investment in new medical equipment can lead to cost savings in the future. In private equity, the J Curve demonstrates how longer-term, often high-risk investments can yield greater returns than immediate, low-risk investments. Finally, in the political realm, the J Curve can be used to illustrate how certain policy interventions can lead to a long-term improvement, despite appearing to worsen the situation in the short term.

The J Curve is a useful tool for determining how an economy will behave in response to certain stimuli. By comparing the performance of certain variables before and after a certain event, it can be an aid to understanding the success or otherwise of an economic decision – and serve as a benchmark against which to measure future changes. As such, the J Curve is invaluable in economic forecasting, providing economists and investors with a guideline for judging the likely effect of their decisions.