Measuring value of economic activity: gdp the best measure of how well the economy is performing, often used for measuring quality of life. Administrative data - by products of government functions such as tax collection. Simultaneously measures total output of goods/services, total income of all individuals, total expenditure of all individuals. Total output produces is purchased, and results in income. Total production = total income = total expenditure. Gdp - the market value of final goods and services produced within an economy in given period of time. Market value - allows adding together unlike items by valuing them at market prices. Anything produced outside the market, ex at home (not purchased) is not counted. Capital goods are final goods since they aren"t used in same period as produced - ie not. Final goods and services doesn"t count goods used for production.