Anyone would agree that slotting–the ideal placement of products in a warehouse–has an enormous effect on the productivity of a distribution center. In a typical picking system, it can mean the difference between 60 and 200 lines per man hour pick rates.

When a warehouse manager suspects poor system performance, the first step is typically to check the real data. Unfortunately, more than 50% of the time, system performance is measured incorrectly. Data is only as good as the methods used to calculate it; if something is measured the wrong way, the results will be wrong. This may lead to the justification of system changes, or even an entirely new system, based on imprecise data.