Remember the Detroit man who walked 34 kilometers to work?

James Robertson's arduous daily journey back and forth to a low-wage factory job, widely reported last month, is just an extreme version of an increasingly common problem: Finding a job near home is getting harder for millions of US citizen workers. And long commutes are especially tough on the poor and on blacks and Hispanics.

A Brookings Institution report on Tuesday finds the number of jobs within typical commuting range dropped 7 percent between 2000 and 2012 in major US metropolitan areas.