NEW YORK (TheStreet) -- The reality of slowing Chinese demand for new cars constitutes a key factor behind the rout in equities of global automakers. 

Weaker auto sales in China have been evident since the spring, though executives have talked reassuringly about being able to match last year's results or at least continue to grow, albeit at a lesser rate than the red-hot pace of the past decade. The past week's performance of global equity markets may reflect a bearish car-buying trend, deeper than previously detected, in the world's biggest vehicle market. 

Shares of General Motors (GM) - Get Report, Ford Motor (F) - Get Report, and Fiat Chrysler Automobiles (FCAU) - Get Reportfell between 4.5% to 6% on Monday. Of the three, GM is most heavily invested and dependent on China, with Ford and FCA not yet among the biggest players. But the slide in share value of all three may portend a belief among investors that a correction in the U.S. stock market could affect the results of all of them. 

Chinese consumer confidence has been badly dented by whipsawing prices in equity markets that have wiped out more than $4 trillion worth of market value. The nation's government has been intervening to try to contain the losses. 

Volkswagen (VLKAF) , another of the top players in China, fell on Monday, as did BMW.

From Hong Kong, Quentin Jones of the Economic Times wrote: "The world's largest car market is shifting down a gear. China no longer promises the super-fast growth and fat margins it once offered." 

In late July, Bob Shanks, Ford's chief financial officer, said the automaker is forecasting a possible absolute decline in the number of vehicles sold in China, the first time for such an event in 17 years. The luxury segment had been hit particularly hard, since it responds more directly to stock-market losses: BMW blamed China for part of the second-quarter drop in profit. Toyota (TM) - Get Report noted in its second-quarter earnings call that sales expenses, incentives and reimbursement to dealers in China, have been rising. 

On Monday, Daimler (DDAIF) , a major factor in the market for Mercedes-Benz luxury cars in China, said it remains confident it will be able to sell 300,000 vehicles in the country this year. Hubertus Troska, head of Daimler in China, said the automaker will invest more in compact cars. Its sales were up 22% over the year earlier through July, a strong month in which it outsold Audi and BMW, its chief rivals. 

Daimler shares were down 4.7% on Monday in European trading. A new Mercedes-Benz long-wheel-base version of its C-Class sedan has proven popular, the company said. It began manufacturing a GLA compact SUV with Chinese partner, BAIC Motor in April. 

New-car buying, long understood as an emblem of confident consumers in the West, now is getting hurt in the East, where that connection is being revealed for the first time.

The writer has no financial interest in any of the companies mentioned.