WASHINGTON (MarketWatch) — Sales at U.S. retailers rose last month on strong demand for cars, trucks and home-improvement products, but spending tapered off at most other retailers after a big bump in demand in April.

Despite the mixed report, the pace of sales in April and May taken together reflect an economy growing at a moderate pace in the spring after the U.S. suffered a sharp contraction in the first quarter. Retail sales account for about one-third of consumer spending, the main engine of U.S. economic activity.

In May, retail sales rose a seasonally adjusted 0.3%, the Commerce Department reported Thursday.

While the increase was smaller than the 0.7% forecast of economists polled by MarketWatch, the government also sharply revised sales in April to show a solid 0.5% gain instead of 0.1% as originally reported. Factoring in the April revision, the increase in sales in May was actually a bit larger than Wall Street had expected.

“The disappointing results for May were tempered a bit by upward revisions to sales in April,” said economist Michael Moran of Daiwa Capital Markets.

With employment rising and many sectors of the economy on an upswing, analysts expect consumers to boost spending and help generate faster U.S. growth in the second quarter and beyond. Economists polled by MarketWatch predict gross domestic product will accelerate to 3.7% in April-to-June period after an estimated 1% decline in the first quarter.

Yet the U.S. retail sector also showed plenty of soft spots in May, with sales falling in virtually every major category except autos and building materials. Sales declined at groceries, bars and restaurants, clothing outlets, electronic and appliance sellers, department stores and companies that sell sporting goods and hobby items.

“The May data show broad weakness outside of the jump in auto sales,” said Stephen Stanley, chief economist of Pierpont Securities and one of the few prominent Wall Street economists who doesn’t believe U.S. growth is ready to surge.

Offsetting those declines was a 1.4% spike in motor-vehicle sales. Auto dealers sold enough cars and trucks to push the level of sales in May to a 16.7 million annual rate — a post-recession high.

Sales also climbed 1.1% at home-improvement stores such as Home Depot HD, -1.70% and Lowe’s LOW, -2.24% that sell building materials. Sales of building materials typically surge in the spring after the end of a winter chill.

Excluding the large auto sector, retail sales grew just 0.1% in May. And sales were flat minus autos and gasoline.

Over the past three months, U.S. retail sales are up 4.3% compared to the same period in 2013. Yet retail sales have historically grown about 6% a year, a sign the economy is still not expanding as fast as it’s capable.

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