The Urban Century

Sometime in 2007, with no announcement and no ceremony, humanity crossed the most consequential line in its settlement history: for the first time, more people lived in cities than outside them. The World Bank's ledger records the moment plainly — the urban share of the world's population edged from 49.9 percent in 2006 to 50.4 in 2007 — and the line has not looked back. It stands at 57.8 percent today.

Run the tape back to 1960 and the scale of the change comes into focus. Then, about a third of humanity — one billion people — lived in cities. Today it is nearly five billion. The era is remembered for its wars and its inventions; measured in people moved, nothing in it compares to this.

The chart below shows how unevenly the urban century arrived. South Korea moved first and fastest among the latecomers, vaulting from 28 percent urban in 1960 past the midline in 1977 to 81 percent today — the settlement pattern of a rich country assembled inside one working life. Brazil, already nearly half-urban in 1960 and past 50 percent by 1967, kept going to 88 percent, more citified than the United States. And Nigeria did something quietly remarkable: a country that was 14 percent urban in the year of its independence is now 64 percent urban — a larger proportional shift than China's.

China is the story the world aggregate cannot contain. In 1960 fewer than one Chinese in five lived in a city, and for the next two decades the share actually sagged — the state held people to the land, and the urban share was lower in 1980 than it had been in 1960. Then the reform era unlocked the factory coast, and the largest migration in recorded history began. China passed the 50 percent mark in 2011 and stands at 66 percent today; its cities now hold roughly 930 million people, more than the entire population of Europe. No forecast made in 1980 imagined it.

Humanity changed its address in a single lifetime.

The holdouts

The great exception is India. The country at the center of this century's population arithmetic is still only 36 percent urban — a share the world as a whole passed back in the 1960s. The absolute numbers are enormous anyway: India's cities hold more than half a billion people, more than the total population of any country on Earth except China and India itself. But the village remains the Indian default in a way it no longer is almost anywhere else of comparable size, and how fast that changes is one of the biggest open variables in the world economy.

Ethiopia sits further back still, at about 24 percent urban. The urban century is not late there; it is early.

The line matters because almost everything else in this magazine's data moves with it. Urbanization tracks the fall of agricultural employment, the rise of schooling, the fertility decline, the growth of income — not perfectly, and not always as cause, but so reliably that the urban share works as a one-number summary of the great transformation. A country's percentage of city-dwellers is a fair first guess at its century.

What remains is the back half. The rich world's lines have flattened in the eighties and nineties of the percentage scale — the S-curve's ceiling — while Africa and South Asia are still on the steep middle stretch. On any plausible continuation of these curves, the next couple of billion city-dwellers arrive overwhelmingly in the places least equipped to house them. The urban century has crossed its midpoint. Its hardest chapters are ahead.

Every figure identifies its source. See SPHRE sources and methodology.