This statistic shows the monthly chained consumer price index from April 2012 to April 2013. The data represents U.S. city averages. The base period was December 1999=100. The chain weighted CPI incorporates the average changes in the quantity of goods purchased, along with standard pricing effects. This allows the chain weighted CPI to reflect situations where customers shift the weight of their purchases from one area of spending to another. The chained consumer price index was at 133.4 in April 2013 reflecting a 33.4 percent increase from the base year 1999.