Real GDP in the context of "Deflation"

Real income is the income of individuals or nations after adjusting for inflation. It is calculated by dividing nominal income by the price level. Real variables such as real income and real GDP are variables that are measured in physical units, while nominal variables such as nominal income and nominal GDP are measured in monetary units. Therefore, real income is a more useful indicator of well-being since it measures the amount of goods and services that can be purchased with the income. Growth of real income is related to real gross national income per capita growth.

According to the classical dichotomy theory, real variables and nominal variables are separate in the long run, so they are not influenced by each other. In other words, if the nominal starting income was 100 and there was 10% inflation (general rise in prices, for example, what cost 10 now costs 11), then with nominal income of still 100, one can buy roughly 9% less; so if nominal income was not adjusted for inflation (did not rise by 10%), real income has dropped by approximately 9%. But if the classical dichotomy holds, nominal income will eventually go up by 10%, leaving real income unchanged from its original value.

An economic expansion is an upturn in the level of economic activity and of the goods and services available. It is a finite period of growth, often measured by a rise in real GDP, that marks a reversal from a previous period, for example, while recovering from a recession. The explanation of fluctuations in aggregate economic activity between expansions and contractions ("booms" and "busts" within the "business cycle") is one of the primary concerns of macroeconomics.

In macroeconomics, the classical dichotomy is the idea, attributed to classical and pre-Keynesian economics, that real and nominal variables can be analyzed separately. To be precise, an economy exhibits the classical dichotomy if real variables such as output and real interest rates can be completely analyzed without considering what is happening to their nominal counterparts, the money value of output and the interest rate. In particular, this means that real GDP and other real variables can be determined without knowing the level of the nominal money supply or the rate of inflation. An economy exhibits the classical dichotomy if money is neutral, affecting only the price level, not real variables. As such, if the classical dichotomy holds, money only affects absolute rather than the relative prices between goods.

The classical dichotomy was integral to the thinking of some pre-Keynesian economists ("money as a veil") as a long-run proposition and is found today in new classical theories of macroeconomics. In new classical macroeconomics there is a short-run Phillips curve which can shift vertically according to the rational expectations being reviewed continuously. In the strict sense, money is not neutral in the short-run, that is, classical dichotomy does not hold, since agents tend to respond to changes in prices and in the quantity of money through changing their supply decisions. However, money should be neutral in the long run, and the classical dichotomy should be restored in the long-run, since there was no relationship between prices and real macroeconomic performance at the data level. This view has serious economic policy consequences. In the long-run, owing to the dichotomy, money is not assumed to be an effective instrument in controlling macroeconomic performance, while in the short-run there is a trade-off between prices and output (or unemployment), but, owing to rational expectations, government cannot exploit it in order to build a systematic countercyclical economic policy.

Neutrality of money is the idea that a change in the money supply affects only nominal variables in the economy such as prices, wages, and exchange rates, with no effect on real variables, like employment, real GDP, and real consumption. Neutrality of money is an important idea in classical economics and is related to the classical dichotomy. It implies that the central bank does not affect the real economy (e.g., the number of jobs, the size of real GDP, the amount of real investment) by creating money. Instead, any increase in the supply of money would be offset by a proportional rise in prices and wages. This assumption underlies some mainstream macroeconomic models (e.g. real business cycle theory, which models the response of the economy to shocks in real variables). However, economists generally find that money is neutral only in the long run; in the short run, price stickiness means changes in the money supply can produce changes in real variables such as employment.

Superneutrality of money is a stronger property than neutrality of money. It holds that not only is the real economy unaffected by the level of the money supply but also that the rate of money supply growth has no effect on real variables. In this case, nominal wages and prices remain proportional to the nominal money supply not only in response to one-time permanent changes in the nominal money supply but also in response to permanent changes in the growth rate of the nominal money supply. Typically superneutrality is addressed in the context of long-run models.