"Now that’s, of course, a big number, and many people are scared of it," says Walden, an economist with N.C. State University's College of Agriculture and Life Sciences. "But it’s actually interesting to know why world population is increasing.

"It’s actually not because households are having more children. In fact, fertility rates are falling worldwide. That is, households are having fewer children.

"But population is going up really for two reasons: One, people are living longer, and number two simply because we have so many households (that) even if each household has fewer children than they did in the past that’s going to swell the population.

"One big implication of this ... is that what’s called the age pyramid -- think of the age pyramid as you have a lot of young people, and then you have fewer middle age people and then very few old people –- that’s going to sort of flatten.

"That is, the projections are that you will have perhaps ... almost just as many older people by the year 2050 as younger people. That’s going to have big implications for many things, like the work force."