In this 2010 TedTalks, at 4:21 Bill Gates says, "First, we've got population. The world today has 6.8 billion people. That's headed up to about nine billion. Now, if we do a really great job on new vaccines, health care, reproductive health services, we could lower that by, perhaps, 10 or 15 percent. But there, we see an increase of about 1.3."

Even though his talk is about innovating new energy industry, this quote is meaningful and taken out of context it is still telling.

https://www.ted.com/talks/bill_gates_innovating_to_zero/transcript#t-289861