But when 5-series intenders settle for a 3-series, the economy is softening.

FORBES: Forecasting The Market With Oddball Indicators

From 2008 to 2011, the Generation Y group grew its share of new-vehicle intenders by 50 percent, to 24 percent, from 16 percent.

FORBES: Baby Boomers Are Past Their Prime, In Car-Buying Years

The GfK study found that 29 percent of Gen Y consumers are small car intenders, vs. 19 percent for Gen X and 19 percent for Baby Boomers.

FORBES: Baby Boomers Are Past Their Prime, In Car-Buying Years