I’m working out an inflation comparison and, annoyingly, the US presents its data in m/m format, whereas the UK and Euro-area present it in y/y. How is y/y data calculated, and is it possible for me to manually look at the m/m figures and work out CPI y/y for US data?
The y/y figure is simply the value this year compared to what it was at the same time last year. You’d need the raw data to be able to do your own calc, but most likely to can find it reported some place. And no, you cannot extrapolate a m/m reading into a y/y one.