Population riddle

THE UNITED NATIONS POPULATION FUND HAS picked October 31 as the day the world will be home to 7 billion people.

For better and worse, it's a milestone.

And there will be more milestones ahead. Fourteen years from now, there are expected to be 8 billion people on the planet. Most of the growth will occur in the world's poorer countries. Proportionally, Europe's population will decline, while Africa's will increase. At around the same time, India will overtake China as the most populous nation on Earth.