Which is correct, baseline finish or forecasted finish?
The Critical Path Length Index (CLPI) like many other EVM metrics are all based on context. It is a measure of the relative efficiency required to complete a contract or a major milestone.
Open full Question Details
Think of a common EVM metric, Estimate at Complete (EAC). There is not a “correct” way to calculate an EAC. An EAC based on the 6 month CPI is no more correct than an EAC based on the cum CPI times the cumulate SPI.
The generic form of CLPI is Remaining Duration plus Float divided by the Remaining Duration. The amount of Float should always be measured against the Baseline Finish Date, but the Remaining Duration of the Critical Path can be calculated using either the Baseline Finish or the Current Finish Date. The key is to be consistent in your calculations and understand what the metric is representing.
For a more detailed insight into CLPI and how the metric can be manipulated I refer you to an article that was published in the Defense Acquisition Research Journal, October 2011 by David C. Bachman:
“Better Schedule Performance Assessments Derived From Integrated Master Plan-Referenced Schedule Metrics”