The co-movement of two or more non-stationary variables over time. If two variables are cointegrated, regression of one variable on the other results in a set of residuals that is stationary. Existence of this long-run equilibrium relationship allows one to impose <a href="search.pl?p=parameter restrictions">parameter restrictions</a> on a <a href="search.pl?p=Vector AutoRegressive model">Vector AutoRegressive model</a> (VAR). The restricted VAR can be expressed in various ways, one of which is the <a href="search.pl?p=error correction model">error correction model</a>. With more than two non-stationary variables, it is possible to have more than one long-run equilibrium relationship among them.<o:p></o:p></P>