12% is not correct.
The 150 economically most significant metropolitan areas around the world are home to about 800 million people, accounting for 12% of the total global population.
Given that large metro areas often are the center of entire countries' economies, their share of global GDP outweighs their population share by a considerable margin.
The world's 150 top metro areas in the Global Metro Monitor, jointly issued by the Brookings Institution and the London School of Economics, reflect a vast variety of living standards, ranging from an annual low average income of $900 a year in Kolkata, India, all the way up to Zurich, Switzerland — the world's richest metro area, with $70,000 in average annual income.
20% is not correct.
The world's 17 largest metro economies together account for about 20% of global GDP. The five largest metro economies are Tokyo (accounting for 3.5% of global GDP), New York (2.4%), London (1.9%), Osaka (1.6%) and Los Angeles (1.5%).
Interestingly, some of the metros around the world with the lowest levels of income and employment growth during the recovery (2009 to 2010) are Athens, Greece; Madrid, Spain; Las Vegas, United States; Dubai, UAE; and Dublin, Ireland — the very metros that were high fliers before the recession (1993 to 2007), and many of which suffered from a bursting of their real estate bubbles.
33% is not correct.
As recently as 1950, around 30% of the world population lived in urban areas. By now, that percentage has risen to over half — and it is expected that about 60% of the world population will live in urban areas by 2030.
Underscoring the economic significance of metro areas, London; Sao Paulo, Brazil; Auckland, New Zealand; and Sofia, Bulgaria, account for about one-third of their respective countries' entire GDPs. Overall, 25 of the 150 metros account for at least one-third of their respective countries' GDPs.
46% is correct.
At 46% of global GDP, the 150 major metro areas account for almost four times more in terms of global GDP as they do in terms of population (12%). This fact underscores just how important metro area economies in particular are as countries around the world seek to find pathways for economic recovery and growth.
The five top performers in terms of income and employment growth in the recovery period (2009 to 2010) were Istanbul, Turkey; Shenzhen, China; Lima, Peru; Singapore; and Santiago, Chile.
While China accounted for four of the top ten performers, Latin America had three metro areas among the top ten. India had five among the top 20, but none among the top ten. Austin, Texas, was the best-performing U.S. metro area (in 26th place among the 150 during the recovery) — and Krakow, Poland, was the top European performer (in 38th place during the recovery).