Auto sales in the U.S. are likely to improve significantly in May based on revival in demand, favorable credits and higher incentives. According to automotive information website Edmunds.com, total sales are expected to jump 31.1% to 1,391,163 vehicles in the month from last year. The website believes that the major automakers are likely to post double-digit growth in sales.

In the past few months, U.S. auto sales continued to be positively affected by strong pent-up demandwith the average age of vehicles on the roads being 11 years. The automakers are increasing the incentive spending in order to boost sales further. In May, average incentive spending was $2,135 per vehicle, up 3.9% from April and 0.6% from May 2011.

Edmunds.com expects Toyota Motor Corp. ( TM - Analyst Report ) , Chrysler and Honda Motor Co. ( HMC - Analyst Report ) to achieve market share gains while Ford Motor Co. ( F - Analyst Report ) , General Motors Company ( GM - Analyst Report ) and Nissan Motor Co. ( NSANY ) will occupy the rest of the market during the month.

In April, U.S. saw a sluggish 2.3% growth in light vehicle sales to 1.18 million units from 1.16 million units in the same month last year. Meanwhile, it rose 9.5% to seasonally adjusted annual rate (SAAR) of 14.42 million units from 13.17 million units in April 2011.

The sluggish growth was attributable to lower sales recorded by the two big players in the industry – GM and Ford – and fewer selling days (due to more Sundays than April last year). But thanks to the fuel-efficient lineups and pent up demand that kept the auto sales recovery on track.