A rep's mean signed forecast miss across quarters, measured at the same week each quarter. Distinct from error, which ignores direction. A rep with low error and high bias is predictably wrong and can be adjusted; one with high error and low bias cannot.
Week-twelve forecasts are always right. Measure at a fixed week, say six of thirteen.
Raw forecast, per-rep adjustment and adjusted total are three lines on one page. The sales leader commits one.
The mean of signed forecast error for a rep over the last four quarters, measured at the same week each quarter.
A rep missed by minus 12, minus 9, minus 15 and minus 11 percent: bias of minus 12. A colleague at plus 6, minus 8, plus 4, minus 5 has the same typical error and no bias.
Only accuracy reported. The sandbagger and the random misser look identical and need opposite conversations.