An increase in male immigrants to Canada is causing a shift in the country’s gender ratio, with the proportion of females decreasing to its smallest level in decades.

The population of adult men grew by 3.4% over the past year, outpacing the 2.9% growth in women. This difference marks the widest spread between the growth rates of the two genders in nearly 50 years of recorded data, Bloomberg quoted an analysis done by Doug Porter, chief economist at the Bank of Montreal.

The disparity is particularly pronounced in the 25-to-44 age group, where men experienced a 4.8% increase compared to a 3.9% rise in women. As of January, there are 141,000 more men than women in this age bracket, a departure from the long-run average difference of zero.

Prime Minister Justin Trudeau has made immigration his main weapon to blunt Canada’s big challenge of an aging and slowing population, and it has also helped fuel economic growth. That drove Canada’s population up at its fastest clip in more than six decades this year, Statistics Canada had said in December last year.

But now a reversal of that trend is gradually taking hold. In the first six months of 2023 some 42,000 individuals departed Canada, adding to 93,818 people who left in 2022 and 85,927 exits in 2021, official data show.

The rate of immigrants leaving Canada hit a two-decade high in 2019, according to a recent report from the Institute for Canadian Citizenship (ICC), an immigration advocacy group. While the numbers went down during pandemic lockdowns, Statistics Canada data shows it is once again rising.

While that is a fraction of the 263,000 who came to the country over the same period, a steady rise in emigration is making some observers wary.

For a nation built on immigrants, a rising trend of people leaving Canada risks undermining one of Prime Minister Justin Trudeau’s government’s signature policies, which granted permanent residency to a record 2.5 million people in just eight years.

An estimated 300,000 to 600,000 people are living in the country without valid documents, many of whom risk deportation because they lack formal status, according to media reports.