Measurement of economic magnitudes using the prices actually prevailing at any given time, for example 2008 gross domestic product at 2008 prices. This may mean the prices in force at some particular date, for example 1 April, or the average of prices observed over the year; in years of high inflation these could differ significantly. Measurement of economic variables in current prices is contrasted with measurement at constant prices. Comparisons in current prices record nominal and not real differences, whereas comparisons in constant prices record real changes.