Update: The December job numbers released this morning continued the same trend described in yesterday’s column. Of the 200,000 new jobs created last month, 78,000 – or nearly 40 percent — were in transportation, warehousing and retail, sectors known for low pay and seasonal hiring. In a far more positive sign, manufacturing gained 23,000 workers in December after four months of little change. A vast expansion of that trend would benefit the middle class tremendously.

WASHINGTON — Between now and November, middle class Americans are going to hear an enormous amount of bragging about job creation.

Mitt Romney will tout his role in the creation of Staples, The Sports Authority and Domino’s, three firms that he says created 100,000 jobs. Barack Obama will say 2.9 million jobs have been created since March 2010, and highlight a surge of 140,000 new private sector jobs in November.

The central question for middle class Americans, however, is: What quality of job is being created? The November job surge, for example, occurred primarily in retail, leisure and hospitality, sectors known for low wages. The other high-growth areas were professional services and health care, where higher education is a central determinant of income. Manufacturing and construction, one of the few areas left in the American economy where members of the middle class without elite educational pedigrees can find strong wages, were moribund. The following chart from the Bureau of Labor Statistics breaks down the numbers.

In a rare moment of bipartisan agreement, Republicans and Democrats both recognize the problem. After years of Democratic politicians complaining about a lack of social mobility for Americans, The New York Times reported this morning that Republican candidates are complaining about the problem as well.