Fewer Canadians are making trips south of the border as a trade war continues between the two countries.

The number of Canadian-resident return trips dropped 31.9 per cent year over year in May, according to Statistics Canada.

Canadian residents returned from 2.3 million trips to the United States, accounting for two-thirds of all trips taken that month.

During that same period, Canadian-resident return trips from overseas increased by just under nine per cent.

Meanwhile, U.S. resident trips to Canada fell for the fourth straight month in May, down 5.6 per cent to two million.

Arrivals by automobile were down seven per cent while air arrivals fell by 1.7 per cent year over year.