Further, the average serial correlation in sales changes for our sample firms is .17 which is also approximately consistent with a random walk. The assumption is not critical to most of our results (the major exception is that earnings is a random walk). Even if sales follow an autoregressive process in first differences, accruals still offset the negative serial I correlation in operating cash flow changes induced by inventory and working capital financing policies. This produces earnings that are better forecasts of future operating cash flows than current operating cash flows and moves earnings changes closer to being serially uncorre1ated. When our.
