North American auto makers built 1,007,282 light vehicles in December, including 435,364 cars and 571,918 light trucks, down 1.5% from year-ago for the only drop in monthly production in 2012.

Fewer official work days in December than in like-2011 contributed to the decline, plus leading manufacturer General Motors cut back on builds.

However, the region’s overall 2012 output was strong, up 17.5% to 15,377,064 units compared with the prior year.

The Detroit Three built 553,181 LVs in December. Ford was up 4.2% to 199,314 units compared with year-ago, while GM was down 7.8% to 193,227, marking the first month that Ford’s output was more than GM’s since December 2009.

GM cut its December production to lower inventory, temporarily closing some plants during the month.

Chrysler assembled 160,640 vehicles in December, down 3.46% from year-ago, for the only monthly decline it saw in the year.

U.S. auto makers built 678,487 units in December, up 1.0% from like-2011. Their full-year total reached 10,061,031, up 19.5%.

Canadian auto manufacturers produced 150,166 LVs in December, down 13.0% from prior-year, and 2,454,064 units for full-year 2012, up 15.5%.

Mexico auto makers made 178,629 LVs in December, down just 0.1% from like-2011, and 2,861,969 for full-year 2012, up 12.5%.