The International Comparison Programme (ICP) is a worldwide statistical project whose purpose is to collect comparative price data from a broad list or basket of products and to compile detailed values for spending-side gross domestic product (GDP) in order to calculate purchasing power parities (PPPs). Using PPPs, rather than market exchange rates, to convert macroeconomic aggregates aids comparison of production across economies and of the well-being of populations in real terms, insofar as they are compared on the basis of the purchasing power of each of the participant countries.