The total value of goods and services produced during a given period within the country, regardless of the nationality of the factors of production. To make comparisons of GDP from one quarter to another, the effect of price variations must be eliminated. Thus, the variation solely in quantities produced is estimated by real GDP, that is, GDP for the period calculated at the price of another period (usually an earlier period), called the base year, such as 1997.The business sector quarterly estimates of real GDP are a Fisher chained index constructed after removing all non-business production as well as the rental on owner occupied dwellings.