Gross domestic product (GDP)

The main measure of an economy’s size. GDP is calculated from the market value of all the finished goods and services within a country’s borders over a set period of time. It has its critics; if a vandal breaks a window, the cost of its repair is an addition to GDP even though human welfare has hardly improved. (For more detail, see this Explainer.) It is also hard to calculate and initial GDP figures are often revised later.