ChatGPT didn’t want to give me this one, I had to ask several times and threaten it!

“In general, revisions to the CPI methodology have tended to lower the reported CPI. According to a study by the Bureau of Labor Statistics, the CPI-U (which measures the overall consumer price index for all urban consumers) has been revised 25 times since its introduction in 1978, and the net effect of all the changes has been to reduce the reported CPI by an average of about 0.2 percentage points per year. However, it's important to note that the magnitude and direction of the impact can vary depending on the specific changes made to the methodology.”