The residential population in the downtown of a number of American big cities grew between 2000 and 2010 and Chicago led the way:

The report found that the number of people living within two miles of Chicago’s City Hall rose 36 percent from 2000 to 2010. Though many of the largest U.S. cities experienced a similar trend in the last decade, Chicago outpaced them all in that category.

More than 48,000 moved to downtown Chicago in the last decade, according to the report. New York City saw a 9.3 percent increase in its downtown population, or about 37,000 people…

Rob Paral, a Chicago demographer, says the city’s downtown population growth reflects several underlying economic factors, including downtown revitalization and an expanding job market.

But though places like the South Loop and West Loop have benefited from the trend, Paral says, its effects quickly fade the farther out you go.

“There’s a big difference between what you see in downtown and what you see in other parts of the city,” he said. “We wish it would be happening within 20 miles of City Hall, but no city has that kind of prosperity.”

In other words: one of the wealthy areas of the city continues to grow while less well-off areas struggle to tackle social problems while facing declining population. I assume this report will be spun by Mayor Emanuel and others to suggest that Chicago is resurgent even in tough economic times. However, a city is not just its downtown.