2.1 Wiki of Social Accounting Matrices

A Social Accounting Matrix (SAM) represents flows of all economic transactions that take place within an economy (regional or national). It is at the core, a matrix representation of the National Accounts for a given country, but can be extended to include non-national accounting flows, and created for whole regions or area. SAMs refer to a single year providing a static picture of the economy.

From: http://en.wikipedia.org/wiki/Social_accounting_matrix