Economics is the social science that has concentrated on the study of the processes of exchange, and more particularly those exchanges that are mediated by money. In other words, in societies in which there is a complex specialisation of labour in the production and distribution of goods and services, economics looks at how these processes are organised and how they work. Macro-economics is concerned with large-scale economic phenomena that apply at national and supra-national level, for example general recessions and expansions of economic activity. Micro-economics is concerned with the processes of exchange between individuals and organisations.