Shoppers slow down in April

NEW YORK (CNNMoney.com) -- Retail sales posted the eighth straight monthly gain in April, but increases were weak after March's data posted the biggest jump on record.

Sales tracker Thomson Reuters, which looks at monthly same-store sales for 28 chains, said Thursday that April sales increased 0.5% over last year. Thomson had expected a 1.7% increase.

Of the 28 retailers, 69% missed Thomson's expectations; 27% beat; and 4% matched.

Same-store sales, or sales at stores open at least a year, are a key indicator of retailers' performance. The data are also important to the overall recovery, since consumer spending fuels two-thirds of the economy.

The weakness in April data was in sharp contrast to the previous month. March's report showed sales increased 9.1% over last year, the biggest monthly gain since Thomson began keeping records in 2000.

The March data got a boost from unusually warm weather, Easter shopping and improved consumer confidence, Thomson said in its report. The calendar shifted the Easter holiday to March this year.

"For year-over-year comp[arisons], it's essential to average the results of [March and April] to get a smoother representation of how the Easter months fared," the Thomson report said, noting the two-month average is a "robust" 4.8% gain.

Teen apparel stores posted the biggest misses in April. That included alternative clothing store Hot Topic (HOTT), which reported sales were down 12.5%, while Thomson expected only a 7.9% drop. The Buckle (BKE) posted a 5.7% decline, while expectations were for a 1.7% jump.

Membership warehouse club Costco (COST, Fortune 500) was among the bright spots, with an 11% gain, but it missed estimates for an increase of 11.2%.