Billesbach and Hayen (1994) compared the. average sales to total inventory ratio during. the 1977-1979 period of 28 firms that had. adopted JIT practices to the average sales to. total inventory ratio during the 1987-1989 period of those 28 firms. Unlike the study reported by Balakrishnan et al. (1996), Billesbach and Hayen (1994) only considered. total inventory and not raw material, WIP,. and finished goods. Their results showed an increase in the average sales to inventory. ratio for 25 out of the 28 firms at a p-value less. than 0.05.