 Testing a variety of different substitutes and outcomes, the researchers found only very weak evidence that substitutes make a difference, and concluded that leader behaviors are the only important variable in predicting employee outcomes.Podsakoff, MacKenzie, and Bommer (1996) conducted a meta-analysis in which they took the results of 22 studies that examined the main effect of substitutes for leadership on the relationship between leader behaviors and subordinate outcomes.They found evidence supporting the theory— taking into account both leader behaviors and the effect of substitutes accounted for more of the variance in subordinate outcomes than taking into account leader behaviors alone.