Vergin (1998) conducted a longitudinal. study by analyzing the changes in the. inventory turnover ratio of 427 firms from. the Fortune 500 list of the largest. corporations in the USA, during the 1986 to. 1995 period, using regression analysis. His results showed that the slope of the. regression model was different from zero at a. statistically significant level of 0.0001. However, he did not classify the firms based. on whether the firms were JIT adopters or. not.