Tokyo's phenomenal growth is largely down to a single factor: migration
from the countryside to the city. It is just one of many to have overtaken
London, which with a population of 7.5 million today doesn't even make the
top 20.
This rural to urban migration can now be seen in scores of cities across the
globe. And it has brought us to a pivotal moment in human history. In 1900,
most people lived in the countryside, with a little over 10 per cent of the
world's population living in cities. From next year, the UN Population
Division predicts that for the first time in history, more people will live in
cities than in the country (see Graph), and the biggest growth will be in
"megacities", with populations over 10 million.