A Producer Price Index (PPI) measures average changes in prices received by domestic producers for their output. It is one of several price indices. Its importance is being undermined by the steady decline in manufactured goods as a share of spending. In the US, the PPI was known as the Wholesale Price Index, or WPI, up to 1978. The PPI is one of the oldest continuous systems of statistical data published by the Bureau of Labor Statistics, as well as one of the oldest economic time series compiled by the Federal Government.