Therefore, the OEI process used in this study is among the most robust used in any program. Figure illustrates the dierence between the OEI and the TD estimates, using the same plot format as Figure . When comparing OEI to TD methods, it is important to note that OEI estimates have no stated uncertainty. Therefore, uncertainty in all comparisons is exclusively from the uncertainty estimate of the TD method. For both TD methods, the operator's inventory is signicantly lower than either of the TD methods at the vast majority of facilities; the OEI is statistically higher than Solution 2 in 1 of 15 comparisons, and statistically higher than Solution 1 in 2 of 28 comparisons. Although TD estimates may have higher uncertainty than shown, logical increases in uncertainty are unlikely to close the gap between the TD and OEI estimates.