Following the Trump administration’s criticism of the Canadian dairy industry, a recent price survey discovered that milk prices across the country vary heavily due to the industry’s supply management system.

Mystery shopping app Field Agent conducted a survey of 171 stores across 18 cities in Canada.

While the average national price per litre of 2 per cent milk when purchased in a four-litre container is $1.22, the price anywhere from 15 to 48 per cent higher in Atlantic Canada. The most expensive city was St. John’s, N.L. at $1.85 a litre in a two-litre container. The cheapest milk was in Sudbury, Ont., at $1.07 a litre in a four-litre container according to the survey.

When looking exclusively at two-litre containers, the most expensive was Toronto ($2.17 per litre) and the least expensive was Charlottetown, P.E.I. ($1.73 per litre).

“At the crux of everything is the fragmented quota system in Canada,” Jeff Doucette with Field Agent Canada explained to CTV Vancouver.

Dairy farmers in Canada are assigned a monthly quota for how much milk to produce. The system was put in place in the 1960s to regulate the dairy supply while ensuring farmers could make a living, which is especially helpful for smaller markets in Canada.

“If we didn’t have a supply managed system in Nova Scotia, we wouldn’t have a dairy industry, ” Nova Scotia’s agriculture minister Keith Colwell told CTV Atlantic on Tuesday.

Despite the perceived benefits, the survey suggested that if there was a national dairy pool, prices across the country would be more even. Currently, British Columbia, Alberta, Saskatchewan, and Manitoba all pool their dairy quotas, while other provinces operate independently.

“If it’s a base milk product it should be relatively comparable from one market to the next across Canada. A national milk pool, beyond levelling the playing field for consumers in different provinces across Canada, would actually make us more competitive with the U.S. market,” Doucette said.

In the U.S., milk prices are even lower. A four-litre jug in Walmart in Buffalo, NY costs about half the Canadian average. The Canadian government imposes minimum prices on milk products, and as a result, imposes high tariffs on cheaper U.S. milk. U.S. president Donald Trump has complained about the tariffs.

Despite the high prices, dairy farmers say the quality of homegrown products is worth it.

“Canadians get a good quality product right across one coast to the other,” dairy farmer Derek Canning told CTV Atlantic.

With files from CTV Atlantic and CTV Vancouver