Is the official inflation rate reliable?

Reader SISMAVISI responds to the Hurriyet Daily News piece on the latest inflation print:

I dont believe in the Turkish Statistical Institute and that the prices go down. if i go to the market for buyin my needs then i see that the prices are not stabil and they are incresing continiuos. So the question is, shall i belive in reality that i see with my own eyes or in unrealistic report of the Turkish Statistical Institute? please answer this!

By the way, as a principle, I do not edit reader comments for spelling or grammar. The reason is that I would like to stick to the original text and I have no desire to act as if my English were better than the readers, as they may be making such errors simply because they are writing too fast. I am already very grateful for reader comments, so I wouldn't even dare to ask them to check their spelling and grammar before they send in their comments.

Anyway, the reader is raising a very important point: Her consumption basket is different than TURKSTAT's, so she may be seeing a different inflation rate. But you can also easily argue that official inflation statistics overshoot real inflation to the extent that the consumption basket is not updated regularly: For example, new products mean that pocket inflation would be lower than official inflation. Similarly, an outdated consumption basket would not take into consideration substitution effects (i.e. the fact that you'd choose your consumption basket in favor of cheaper products).

And suppose that the reader is right, TURKSTAT inflation is indeed higher than official inflation. Obviously, official inflation would be understating real inflation. But as long as TURKSTAT makes the same measurement error each month, this wouldn't make much of a difference; for example, although you'd know that prices did not fall last month, you'd at least know that the rate of price increases is falling. That's an important piece of information by itself.