Detroit ? Shoppers are snapping up cars and trucks so quickly that General Motors Co. is boosting production for the rest of the year to keep up with Cash for Clunkers demand.

It’s another sign that automakers believe consumers are returning to showrooms after a yearlong slump. Ford Motor Co. last week moved to increase its output, and other automakers took similar action earlier in the month.

Confidence among manufacturers is up, even though analysts predict that demand from Cash for Clunkers is waning.

GM said Tuesday it would add 60,000 vehicles to its production schedule in the third and fourth quarters and bring back about 1,350 laid-off workers. The company now plans to make 535,000 cars and trucks during July-September.