DETROIT — In the race to claim ever-higher fuel-economy numbers and keep up with government regulations, automakers are rolling out hybrids and electric cars aplenty at this week’s Detroit auto show.

If only buyers were arriving as fast as the cars.

Hybrid sales waned as gasoline prices ebbed in 2011, declining to 2.2 percent of the market from 2.4 percent a year earlier, according to the research firm LMC Automotive. Meanwhile, sales of the Nissan Leaf electric car and the Chevrolet Volt plug-in each fell short of expectations.

Analysts do not expect the segment to grow significantly this year: the combination of gas prices below $4 a gallon and higher upfront costs for the cars is not attracting consumers.