Project Schedule Variance (PSV) is a measure of the extent to which projects are delivered on schedule.
Project Schedule Variance (PSV) = SCT - ACT
Where ACT is the Actual Completion Time
And SCT is the Scheduled Completion Time
This indicator is included in the book: Key Performance Indicators - the 75+ measures every manager needs to know, which contains an in-depth description of this KPI, as well as practical advice on data collection, calculations, target setting, and actual usage.