Brain power improves by brain use, just as our bodily strength grows with exercise. And there is no doubt that a large proportion of the female population, from school days to late middle age, now have very complicated lives indeed.

Almost half of the population of the world lives in rural regions and mostly in a state of poverty. Such inequalities in human development have been one of the primary reasons for unrest and, in some parts of the world, even violence.

We seek the right to play our part in advancing the cause of national defense and national unity. But certainly, there can be no true national unity where one-tenth of the population is denied their basic rights as American citizens.

One of the biggest challenges for the MENA region is unemployment coupled with high population growth rates. The World Bank is committed to supporting infrastructure projects that will help with job creation across the region.

It is undeniable that the looming environmental crisis is partly the consequence of population growth.

I have always found it difficult to wrap my head around population policies.

I reside in a new colony for the Chinese-singing banjo player, with a population of one. At least I have something I have to do with my life.

With a tree, all the growth takes place at the growing tips. Humanity is exactly the same. All the growth takes place in the growing tip: among that one percent of the population. It's made up of pioneers, the beginners. That's where the action is.

The idea of confidence, of the emotions of the population, is an incredibly important one in economics. John Maynard Keynes called it 'animal spirit.' And if people are feeling generally good about the future, they're more likely to spend money, to start new companies; companies are more likely to hire people, make investments.

For the better part of two centuries, outsiders have been offering explanations that range from racist to learned-sounding - the supposed inferiority of blacks, the heritage of slavery, overpopulation - for why Haiti remains the poorest country in the Western Hemisphere.