Gross domestic product
Gross domestic product (GDP) is a monetary measure of the market value of all the final goods and services produced in a period of time, often annually 
GDP (nominal) per capita does not, however, reflect differences in the cost of living and the inflation rates of the countries; therefore using a basis of GDP per capita at purchasing power parity (PPP) is arguably more useful when comparing differences in living standards between nations.
GDP density
GDP Density is a measure of economic activity by area. It is expressed as GDP per square kilometer and can be calculated by multiplying GDP per capita of an area by the population density of that area. Amongst other uses it demonstrates the effects of geography on economy.