The habitable zone is the region of a planetary system which is neither too hot nor too cold - such that water on the surface of a planet will neither evaporate nor freeze, but instead can stay liquid.

BBC: NEWS | Science/Nature | Earth-like planets may be common

But for the moment, Asians and Latinos are enjoying fertility that is neither too hot, nor too cold.

ECONOMIST: Lower fertility is changing the world for the better

Until this summer, their favourite was Goldilocks: the American economy, they claimed, was neither too hot, nor too cold, but just right.

ECONOMIST: Once upon a time on Wall Street | The