It keeps the auto industry on its toes, deciding which cars will sell, how many to build, how much money the public will pay - and too often it fumbles the ball.
In 1981, for example, the General Motors Pontiac Division opted to get out of the big-car business altogether in the United States. Even the demise of the V-8 engine was widely announced. Gasoline prices were on the rise and the long-term supply in doubt.
What to do? Build smaller, more-fuel-efficient cars. Obviously. Pontiac was on solid ground.
But now, with the sharp rise in big-car sales over the last few months, Pontiac has been forced into some fancy footwork. Thus, not wanting to lose any potential customers because it didn't have a full-size car, it opted to ship in a car from its Oshawa, Ontario, assembly plant.
Enter the Pontiac Parisienne and - voila!m Pontiac is back in the big-car business again.
It now seems that it was a good move.
The Parisienne is the Pontiac equivalent of the Chevrolet Caprice-Impala, Buick LeSabre, and Oldsmobile 88. In other words, it's a B-body car, downsized in 1977, face-lifted in '80, but little changed since then.
To show how strong the big-car market really is, Pontiac expects to sell 16, 000 Parisiennes in the United States (49 states, excluding California) between early May and the end of the '83-model year in September. In '84, however, the car will be ready for sale in California and the division projects some 60,000 sales overall.
No one wants to give up 60,000 sales, given the state of the auto business these days.
Where does the Parisienne sell best? A Pontiac spokesman replies: ''The car is strong in the Midwest, but weak on both coasts.'' The West Coast, of course - especially California - is ''import country.''
To assure availability to meet the expected demand, the Parisienne will quit the Oshawa plant in the fall and be built instead at the GM assembly plant in Fairfax, Kan.
The 3,400-pound car is strictly conventional, with rear-drive propulsion and the handling and road feel of the large car that it is. It makes no attempt to image an import. It is, on the other hand, comfortable - even luxurious - and is designed for the long haul. Simply put, it's a highway car in every way.
The Parisienne comes as a 4-door sedan, upscale brougham sedan, and brougham 8-passenger wagon. Wheelbase is 115 inches. At 215 inches overall, the wagon is three inches longer than the sedan. The sedan trunk, with a capacity of 21 cubic feet, is huge. The sedan fuel-tank capacity is 25 gallons (27 gallons with the diesel); the wagon tank holds 22 gallons.
The size of the fuel tank should say something about its mileage.
Standard engine is a 3.8-liter V-6 in the sedan, but 5-liter and 5.7-liter V- 8 diesel are options. Base engine in the wagon is the 5-liter V-8 with the diesel as an option.
Base price for the 4-door sedan is $9,609, plus another $270 for the upscale brougham. A well-equipped wagon goes out the door at $13,000 plus.
The Parisienne is all ''plus'' business for Pontiac - something it hadn't counted on when the '83-model year began last fall. It shows how fickle the American car-buying public is these days. Stable gas prices and a plentiful supply has muddied the guessing game in Detroit.
When will it shift again? If anyone knows, tell Detroit.