Exogeneity

Exogeneity refers to a variable’s status within a multivariable model. A variable in a model is exogenous if it is otherwise external to the model; in other words, no other variables in the model affect it causally. The term derives from the Greek words exo, meaning “outside,” and gignomai, meaning “produce.” Exogeneity suggests that the production of a variable is outside the control of the rest of the model.

The inverse of exogeneity is called endogeneity. A variable is endogenous if its value is dependent on other variables in the model. This may be a simple causal relationship: For example, if variable A causes variable B, then variable B will be endogenous in any model also containing variable A. However, it could be a more complex ...