Sales at Wal-Mart again outperformed its competitors in May, suggesting that it the US discount retailer is set to benefit greatly from federal tax refunds aimed at stimulating the economy.

Wal-Mart’s US outlets open at least a year saw sales rise 4 per cent, supported by strong activity in basic goods, including groceries and pharmacy products. Including its Sam’s Club discount warehouse stores, comparable sales rose 3.9 per cent, against the retailer’s original forecast of an increase in the flat-to-2 per cent range.