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.