Slower restocking could weigh on economic growth in the April-June quarter because it means companies ordered fewer factory goods. But the strong sales gain suggests companies may have to order more goods in the coming months to keep up with demand. That could drive more economic growth in the second half of the year.
Many analysts think economic growth has slowed to an annual rate of around 1 percent or even less in the April-June quarter. That would lower than the subpar 1.8 percent annual rate from January through March.
Economists expect growth should rebound in the second half of the year to a roughly 2.5 percent annual rate as the effects of federal tax hikes and government spending cuts fade.
The May increase brought total stockpiles to a seasonally adjusted $1.66 trillion. That's up just 3.8 percent from May 2012.
Wholesalers cut their stockpiles 0.5 percent, while manufacturers' inventories were unchanged in May. Retail stockpiles rose 0.6 percent.
Sales at the wholesale level rose 1.6 percent to lead all categories. Sales at manufacturers and retailers increased slightly below that level.
A separate report Monday showed that retail sales slowed to a modest 0.4 percent increase in June.
The brighter second half outlook is bolstered by steady job growth, which has kept consumers spending. Employers have added 202,000 jobs a month through the first six months of this year. That's up from 180,000 in the previous six months.
The increase in hiring has helped overall income grow, offsetting some of the drag from higher taxes.