For how long is a given PPI relevant and accurate?

As noted in each PPI Design Documentation, it is not possible to know the extent to which a given scorecard will become inaccurate over time. The change in accuracy depends on the overall change in the economic situation of each country; this change could happen very quickly or could progress more slowly. The goal is to update each PPI every five years, which is generally how often countries update their national household survey, and meeting that goal is dependent on data availability, funding and interest.