Inflation or deflation complicates GNP, because GNP is a price times-quantity figure. The changes either in price level or the change in output produced may affect the size of GNP. Then there rises a distinction between nominal GNP and real GNP. The nominal GNP is the representation of GNP in monetary terms while the real GNP is the representation of GNP is quantity or in physical terms. Broadly, the nominal or current price GNP measures the value output at the prices prevailing in the period during which the output is produced. While the real GNP or constant price GNP measures the output produced in any period at the prices of some base year. Real GNP which values the output produced in different years at the same prices implies an estimate of the real or physical change in production or output between any specified years. If we assume 2000 as a base year, it will serve as base year for real output measurement. US nominal GNP was $4864 billion 1988 and it was $1598 billion 1975.
Thus nominal GNP grew at an average rate of 8.9% during the period 1975 – 1988. While if we measure the value of output produced in a year say 1990 on the prices of a gives year say 1982 this will be case of real GNP. US real GNP was $3996 billion in 1988 and $2695 billion in 1975. This shows that real grew at an average of 3.1% per year over the period. If we divide real GNP by population 246 million people in 1988 in US i.e. we divide $3996 billion by 246 million population we get per capita real GNP which was $1644 per member of the population.
From above figures we see that in US nominal GNP has risen much more rapidly then real GNP. The increase in nominal incomes as compared to real income is attributed to inflation. The difference in growth rate of nominal GNP (8.9%) and the real GNP (3.1%) represents the inflation (5.8%). In other words, the nominal increase in GNP is due to price-like-inflation.