The information below relates only to when "Equity" is selected as the active Compensation Type.
Equity differentials are calculated using only those incumbents for which equity data is submitted (i.e. a much smaller population than those for which salary is submitted). It is this headcount which is used when Equity is selected as the compensation type.
In order to understand the relationship between the total headcount available and the headcount for equity, the Equity Participation feature is available.
With Compensation Type switched to Equity, simply hover over any location in the differentials chart. Equity Participation is listed below Headcount in the tooltip.