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a simple rule to be implemented. We suggest that a simple but more accurate rule can be derived by dividing the quadrant diagonally into two. In this case, the rule is to use SBA whenever v42 (3/2)p. This approximation is also shown in Figure 2. Since a is usually small (less than 0.3) for intermittent demand data, this approximation is quite good. In any case, the comparative advantage of one method over the other in the space between the approximate rule and the true boundary will be small. One of the assumptions underlying the SBC analysis (and Croston’s (1972) original analysis) is that it assumes that the demand values are independent. This is clearly never true, and if it was true we would simply use the historical mean as the best predictor rather than any more sophisticated forecasting method. In fact, it has recently been shown by Shenstone and Hyndman (2005) that Croston’s method (as originally proposed in 1972) and related methods cannot be optimal for any time series of demand, regardless of their time series properties. Consequently, we suggest that a more useful line of research may be to find forecasting methods that are optimal assuming realistic properties of demand time series.