The United Nations says that by the end of October, the world's population will surpass seven billion. The world population is now growing by roughly 80 million people per year. The tiny African nation of Zambia is among many nations around the world experiencing a population boom. Thirteen million people now live in Zambia, compared to just 3 million in 1964 — and the U.N. expects that number to triple by 2050, with perhaps over 100 million people living there by the end of the century. Fergus Walsh, correspondent for the BBC, reports on Zambia's population boom.