"TREND FORECAST: Automotive insiders in Detroit, quick to spot a trend or to start one, say the next great market for new cars is the teenage child. First the car was a family purchase, they say, and next it was a second car, for the wife. Now it is a third new car, for junior. They point to the large number of Mustangs, MGs, Corvairs and Triumphs that are being given teenage boys and girls as Christmas presents and graduation gifts. Many children have their own credit cards, and in fact a new credit system for teens is already in operation ....."