WASHINGTON » A private survey shows U.S. businesses increased hiring in January compared with a revised December reading.

Payroll processor ADP said today that employers added 192,000 jobs in January. That is more than December’s revised number of 185,000, which had initially been reported at 215,000.

The ADP report is derived from actual payroll data and tracks total nonfarm private employment each month. The increase in hiring occurred after Congress and the Obama administration reached an agreement on Jan. 1 to avoid sharp tax increases and across-the-board government spending cuts.

The ADP report showed that most of the gains came from small businesses with 49 or fewer employers. This group of firms added 115,000 jobs in January. Medium businesses, those with 50 to 499 employees, added 79,000 jobs during the month while large businesses cut 2,000 employees.

In a separate report today, the government said that the overall economy shrank from October through December at an annual rate of 0.1 percent. The weakness came from the biggest cut in defense spending in 40 years, fewer exports and sluggish growth in company stockpiles. The 0.1 percent drop in the gross domestic product in the fourth quarter was a sharp slowdown from 3.1 percent growth in the July-September period.