Some things you can't buy online :
Groceries, gasoline, electricity, heating oil, natural gas, water.
Let's see...
CPI, CPI, CPI, CPI, CPI and--
you guessed it--CPI.
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Handbook of Methods - (
http://www.bls.gov/opub/hom/pdf/homch17.pdf) Understanding the CPI: Frequently Asked Questions - (
http://stats.bls.gov:80/cpi/cpifaq.htm)
The Consumer Price Index for All Urban Consumers: All Items (CPIAUCSL) is a measure of the average monthly change in the price for goods and services paid by urban consumers between any two time periods.(1) It can also represent the buying habits of urban consumers. This particular index includes roughly 88 percent of the total population, accounting for wage earners, clerical workers, technical workers, self-employed, short-term workers, unemployed, retirees, and those not in the labor force.(1)
The CPIs are based on prices for food, clothing, shelter, and fuels; transportation fares;
service fees (e.g., water and sewer service); and sales taxes. Prices are collected monthly from about
4,000 housing units and approximately
26,000 retail establishments across
87 urban areas.(1) To calculate the index, price changes are averaged with weights representing their importance in the spending of the particular group. The index measures price changes (as a percent change) from a predetermined reference date.(1) In addition to the original unadjusted index distributed, the Bureau of Labor Statistics also releases a seasonally adjusted index. The unadjusted series reflects all factors that may influence a change in prices. However, it can be very useful to look at the seasonally adjusted CPI, which removes the effects of seasonal changes, such as weather, school year, production cycles, and holidays.(1)
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Now here's the kicker, chief; the CPI and BPP are correlated, do you agree? Yet they are measuring the environment differently.
Two sources of data saying essentially the same thing. One using a massive set of raw price data on
whatever and the other a stratified random sample with a mere 30000 respondents.
Can you think of a third way to measure it all?