Does the PPI measure impact?

The PPI supports assertions of impact but cannot prove it alone. The PPI is a measurement tool, similar to a ruler. A ruler can be used to measure someone’s height at two separate times and show that someone has grown, but the measurements don't indicate how. The ruler cannot attribute the increase in height to any particular cause. Likewise, a program aimed at alleviating poverty can measure poverty levels over time, but it cannot use the PPI alone to measure its success. However, the PPI can be used as an integral component of an impact evaluation framework that assesses projects serving the poor. With the PPI and other data obtained through such a framework, managers can make assumptions about causality that inform their decisions.