> They regularly modify the list of items in the cart, meaning the data isn't reliable over time. It may not be reliable over time, but it is reliable over sho

> They regularly modify the list of items in the cart, meaning the data isn't reliable over time. It may not be reliable over time, but it is reliable over shorter time periods. If the basket is not changed for a few years, then the month-by-month changes in CPI are generally judged as reliable, or as reliable as what is out there. It is when you try to look over a 10, 20, 30 year period where you begin to run into trouble.