Seems to me like you are talking about Cohort Analysis: http://www.avc.com/a_vc/2009/10/the-cohort-analysis.html http://www.avc.com/a_vc/2009/10/the-cohort-anal

Seems to me like you are talking about Cohort Analysis: http://www.avc.com/a_vc/2009/10/the-cohort-analysis.html http://www.avc.com/a_vc/2009/10/the-cohort-analysis.html But you are right, a tool for this would be nice.