National accounts or national account systems (NAS) are the implementation of complete and consistent accounting techniques for measuring the economic activity of a nation. These include detailed underlying measures that rely on double-entry accounting. By design, such accounting makes the totals on both sides of an account equal even though they each measure different characteristics, for example production and the income from it. As a method, the subject is termed national accounting or, more generally, social accounting. Stated otherwise, national accounts as systems may be distinguished from the economic data associated with those systems. While sharing many common principles with business accounting, national accounts are based on economic concepts. One conceptual construct for representing flows of all economic transactions that take place in an economy is a social accounting matrix with accounts in each respective row-column entry.