CPI (Consumer Price Index)

A measure of the average change in prices paid by urban consumers for a basket of goods and services, published monthly by the Bureau of Labor Statistics. CPI is the most widely watched inflation gauge and a primary input for Federal Reserve interest rate decisions. On CPI release days, markets can swing violently -- a reading even 0.1% above or below expectations can move the S&P 500 by 1-2% within minutes as traders reprice the path of monetary policy.