MONTREAL -- Oil workers just aren't drinking like they used to.

Molson Coors Brewing Co. blames a sluggish economy for a big drop in beer sales in Alberta, Newfoundland and Labrador, and Saskatchewan.

Customers are abandoning higher-priced premium beers for economy brands, the beer giant says.

"The consumer is under pressure," Stewart Glendinning, chief executive of Molson Coors Canada, said Thursday during a conference call on the company's fourth-quarter and 2015 results.

"And if you add to that the fact that consumer debt in Canada is at an all-time high, it's made for quite a difficult recipe in some of those provinces."

Molson said its sales volume decreased 5.4% across Canada in the fourth quarter. In January, retail store sales fell by more than 10%.

Part of that decrease can also be attributed to higher food prices, Glendinning said, which could have forced beer lovers to choose between groceries and brewskies.

Sales volumes for Coors Light were also reduced in Quebec by the brewer's decision to raise prices for its flagship brand.

Molson Coors said its net income plummeted 65% to US$32.8 million in the fourth quarter because of lower sales, currency fluctuations and reduced income from operations in Canada and the United States.