Online, catalog and other nonstore retailers continue increase their sales faster than merchants that operate stores.

The U.S. Commerce Department reported Wednesday  totalretail sales excluding motor vehicles and parts grew to $377.126 billion in May, up 3.8% from $363.187 billion during May 2016, but down 0.3% from $378.103 billion in April 2017. Nonstore retail sales, which mainly take place online, totaled $51.552 billion during May, up 10.2% from $46.801 billion in May 2016 and up 0.8% from $51.147 billion in April.

That means nonstore sales accounted for 34.1% of retail growth in May, though only 13.7% of sales.

“As we expected, e-commerce remains a bright spot with nonstore retailers registering a 0.8% growth over April, as consumers increasingly are shopping online,” writes Mickey Chadha, a vice president at Moody’s Investors Service. “However, despite a weaker-than-expected sequential sales growth number in May, the year over year adjusted retail sales growth ex-gasoline in May was still a relatively healthy 3.8%, which is line with our 3%-4% year over year retail sales growth forecast for 2017.”

At least one analyst thinks the numbers should be more skewed in favor of online and nonstore sales.

“They’re clearly underestimating the magnitude of the shift towards online retailing,” says Joe Brusuelas, chief economist at audit, tax, and consulting firm RSM. “It only showed half a billion increase (month over month), so we’re really underestimating on a monthly basis. I think that the rate of business formation in the online space within retail categories presents a challenge in capturing new sales from new firms. Because so many of these firms are not publicly held, they may not be providing up to date information on the pace of sales at their firms. There are so many online markets these days.”

Separately, the National Retail Federation reported that overall retail sales grew by 5.3% year-over-year and 0.6% on a month-over-month basis, while online and nonstore sales posted gains of 12.4% year over year and 0.8% month over month. The NRF bases its estimates on retail sales data provided by the Commerce Department, but removes sales of gasoline, automobiles, and restaurants.

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“While the month-to-month comparisons may be unimpressive, current trends in retail sales growth are healthy,” NRF chief economist Jack Kleinhenz said. “It is important to note that retail sales over the past three months are four percent higher than they were during the same three-month period last year.