If you look at food and energy over long periods, they work nicely.

The catch is look at something like eggs in the last few months. Was the doubling of egg prices evidence that prices across the board were going up, or was it an anomaly that corrected quickly? We'd be foolish to think that we were looking at an at large inflationary trend when they went up, or conversely, that there was a deflationary trend at large when they came back down.