Economics is the study of how societies allocate scarce resources to produce and distribute goods and services. It can be studied on both a macro and micro level. On a macro level, economists examine issues like GDP, unemployment, fiscal and monetary policy for entire nations. On a micro level, economists analyze how individuals and firms make decisions and interact in the marketplace. The main types of economic systems are traditional, command, market and mixed economies which differ in how resources are owned and allocated. Scarcity is a core economic concept that refers to unlimited wants exceeding limited resources, requiring choices about allocation.