The standard deviation divided by the mean. It is a measure of relative variation and is sometimes used to make comparisons across variables expressed in different units. It is useful in the analysis of relationships in econometric or judgmental bootstrapping models. Without variation in the data, one may falsely conclude that a variable in a regression analysis is unimportant for forecasting. Check the coefficients of variation to see whether the dependent and explanatory variables have fluctuated substantially. If they have not, seek other ways of estimating the relationships. For example, one might use other time-series, cross-sectional, longitudinalor simulated data. Alternatively, one could use a priori estimates as relationships, basing these on prior research or on domain knowledge.