The CPI, the PPI, and the GDP Deflator As the figure shows, the three different measures of inflation, the PPI (orange), the CPI (green), and the GDP deflator (purple), usually move closely together. Each reveals a drastic acceleration of inflation during the 1970s and a return to relative price stability in the 1990s. With the exception of a brief period of deflation in 2009, prices have remained stable from 2000 to 2013. Sources: Bureau of Labor Statistics; Bureau of Economic Analysis.