Is it possible for total consumption to go up but per capita consumption to go down?

Question

Stumped. Looking at US wheat consumption data since 2002. Total wheat consumption is negatively correlated with per capita wheat consumption (R=-.2). My intuition is that this has something to do with wheat consumption not being evenly distributed by consumer affluence. i.e. The top 20% don't eat wheat at all and the bottom 20% eat more wheat than average. But, I still can't connect how this would cause per capita consumption and total consumption to diverge. Any ideas? That is, how can total wheat consumption go down in a year when per capita wheat consumption goes up? Thanks!

Answer 1

Per capita consumption is total consumption divided by population. If the population rises faster than the total you can have the total increase and the per capita decrease.

Answer 2

If the population rises then if peoples' behaviour is unchanged then total consumption increases but obviously per capita consumption remains the same. There could be many reasons why behaviour changes. An epidemic of gluten intolerance, or maybe people are getting richer thus chose to spend there money on more expensive alternatives. In short, beware of time series data.