Link here: http://en.wikipedia.org/wiki/Consumer_price_index
The CPI is a statistical estimate constructed using the prices of a sample of representative items whose prices are collected periodically.
This is the methodology used ever since it was compiled for the first time and still is and most likely will always be. And the reason for this is simple. The impossibility of interviewing the whole population.
You may say that the sample is not representative, but that is another matter.
The problem with you guys is that your talk is just hydrogen based flatulence.
Ha, in case your complaint is about the size of the sample, here is the link: