The problem with that specific example isn't that there are less white people, there are actually more white people now than at any point in history. Rather, what's happened is that people in third world nations, mostly in Africa, have had population explosions.

A lower percentage doesn't always equate to a lower number. It can also, as is the case here, indicate that it just means another specific percentage of whatever your measuring is growing at a faster rate for that specific period of time.