????When automakers reported their sales for April, most industry watchers were bullish about the results.

????"There is no question that the auto industry is climbing out of last year's pit," wrote John K. Teahen of Automotive News.

????DeutscheBank analyst Rod Lache noted that sales, which came in at an annual rate of 11.2 million, were 20% ahead of a year ago, and reported that consumer sentiment was the best it had been since September, 2007.

????He believes that the industry is headed toward sales of about 11.5 million vehicles, a level that should be profitable for most automakers.

????But overlooked by most observers, however, is a change in buyer preferences that could make this upturn in this highly cyclical industry a lot less profitable than the last one.

????"Consumer downshifting into smaller, and arguably less profitable segments, provides a weak foundation for a robust net income outlook," says Warren Browne, a General Motors executive turned analyst based in Detroit.

????As he points out, volume growth is mostly coming in small and mid-size segments that historically return profits that are small or non-existent. Through April, these two segments represented 38.2% of light vehicle sales, compared with 36% during the same period a year ago.

????Meanwhile, light truck segments that produce higher profits have remained flat or lost share. That includes large and small pickups, large and small vans, and small and mid-size sport-utility vehicles.

????Says Browne, "Manufacturers need more growth in large cars, mid-SUVs and full-size pickups to get into the real profit zone."

????Analyst Jessica Caldwell of Edmunds.com agrees. She notes that the market share of subcompacts like the Honda Fit and Nissan Versa has doubled in the past eight years. She adds that they can be "a little shaky on profitability.

????You can see the evidence of the changes in the list of the ten best selling vehicles of the month.

????Except for those two hearty perennials, the Ford F-series and Chevy Silverado pickups, and the full-size Honda (HMC) Accord, the other seven are on the small side.

????The Toyota Corolla ranks fourth, Honda's Civic is sixth, Ford Fusion comes in seventh, and the Honda CR-V is tenth.

????There are some exceptions. After redesigning the full-size Taurus inside and out, Ford sold more than 6,000 in April at prices of up to $40,000.

????That consumers are thinking small isn't entirely due to gasoline prices or the economy. Analyst Caldwell attributes it partly to new market entrants and new features creating consumer interest. Both GM and Ford (F, Fortune 500) for instance, are introducing important new subcompacts this year: the Chevy Cruze and Ford Fiesta.

????Browne remains relatively pessimistic about car sales for the rest of the year, saying downward pressure will come from high unemployment, low housing starts, and weak consumer confidence.

????He expects manufacturers to sell just 11.6 million cars and trucks this year. While that is up 11% from 2009's dismal performance, it is a far cry from the 16 million to 17 million that was considered normal just a few years ago.

????And if the big stuff isn't selling, that could double the pain.