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.
Economic integration
Dynamic analysis has started with a new definition of gross domestic product (GDP), as a difference between aggregate revenues of sectors and investment (a modification of the value added definition of the GDP). It was possible to analytically prove that all the states gain from economic unification, with larger states receiving less growth of GDP and productivity, and vice versa concerning the benefit to lesser states. Although this fact has been empirically known for decades, now it was also shown as being mathematically correct.