This might be a very trivial question; however I can't seem to find a very useful answer for this.
Problem:
How are the weights of the various household items in the Consumer Price Index (C.P.I.) basket decided, i.e., how are they re-evaluated every year? Is it done manually or automatically?
If its done manually, then how can they be sure (i.e., what methods, statistical or mathematical) that the weights represent the general average consumption of that item in the household? Else, if its done automatically, then what is the strategy (i.e., what sort of algorithms or data structures) used to ensure the accuracy of the weights.