Three important caveats should be considered in interpreting the analytical results of this investigation. First, we did not systematically examine the life-cycle of the sample firms selected for this study because the classification of firm life-cycle stage is complicated and controversial (Quinn and Cameron, 1983). Second, the variables used in this study did not come out of a fully developed supply side model of the firm. Establishing the theoretical models is thus an important direction for future research. Third, this study uses U.S. S&P firms, and future work in this area could examine a range of countries.