DETROIT WILL DRIVE THE GNP UP -- AND THEN DOWN.

Focuses on the turmoil in the U.S. automobile industry. Report that auto makers will be pushing hard to build up an inventory cushion of cars to sell before the United Auto Workers' contract expires on September 15; Opinion that if the contract dispute is settled without a walkout, the auto makers will have to cut output to get inventories of unsold cars back to normal; Reports that a prolonged strike could lower gross national product growth in the fourth quarter by 1.4 percentage points.