The input to CPI is secret shoppers visiting a variety of retail outlets, and buying things (or write down the advertised prices for things) without telling the

The input to CPI is secret shoppers visiting a variety of retail outlets, and buying things (or write down the advertised prices for things) without telling the retail outlet what they’re doing. Publishing the particular products looked at, or even the particular stores visited, would invite market manipulation of the CPI figure by re-pricing the included goods.