Here is an interesting blog I found through Reddit. This is an interview with an economist who is talking about how the government cooks their numbers when they provide economic indicators and numbers. Interesting and depressing reading.
http://carolynbaker.net/site/content/view/1075/1/When it became popularly used in auto-union contracts after WWII, the concept of the Consumer Price Index was fairly simple. But they wanted to measure changes in the cost of living, and they needed to maintain a constant standard of living. That was the traditional definition; the way the CPI had been designed.
That held pretty much in place until we got into the 1990s when Alan Greenspan and Michael Boskin, the head of The Council of Economic Advisors for the first Bush Administration, started talking about how the CPI really overstated inflation. The rationale was that when steak goes up in price, people buy more hamburger instead of steak; therefore you should reflect the substitution in the CPI.
That is not the concept of a constant standard of living; it is the concept of a declining standard of living that has no value to anyone other than politicians in Washington. They succeeded in reducing the reported level of inflation, which reduced cost-of-living adjustments in Social Security checks. Because of the changes in the 1990s, our Social Security checks are about half what they should be!