Originally published in the Ottawa Citizen, 2010

Why worry about how many babies Canadians have? If the country needs more people, we can loosen the tap on immigration. Problem solved.

Anyone who has ever suggested people should be concerned about Canada's fertility rate -- which is far below what is needed to maintain the existing population -- has heard this response. There are almost seven billion people on the planet. Why do we need to make more?

I wish it were that simple. But it's not.

There are two big reasons why immigration is no solution to our low fertility rate. The first comes from the nature of the problem.

The demographic dilemma we face is not -- at least not in the next 30 years -- population decline. It is population aging.

On average, Canadians are getting much older. The number of workers hanging up their skates is rising. Thanks to the aging of the baby boom, that trend will soon accelerate.

Inevitably, that means the size of the retired population will grow relative to the working-age population. In 1970, the retiree population was only 15 per cent as big as the working-age population. In 2005, that had grown only modestly to 20 per cent. But over the next several decades, it will double -- so instead of five working-age Canadians for every one retiree, there will be 2.5. And that trend will continue. By mid-century, there would be two workers for every retiree.

Who will pay for health care and other social services? Who will keep pensions afloat? By 2030, there's a good chance workers will enjoy steadily rising wages thanks to chronic labour shortages, but that money won't go into their pockets. It will go to governments -- which will raise taxes to punishing levels to keep retiree supports from collapsing.

So what matters here is not the absolute numbers of people in the population. It's the ratio of workers to retirees. And many studies have shown that, for a host of reasons, feasible levels of immigration can do little to change the worker-to-retiree ratio.

It's a counter-intuitive result but the numbers don't lie. One C.D. Howe study imagined a huge increase in immigration and projected Canada's future population. Result: a big increase in the total population but little change in the age distribution. Then the analysts imagined draconian policy changes that favoured younger immigrants. Result: little change.

So the analysts asked what would it take to maintain the ratio of workers to retirees? Answer: Immigration would have to more than triple almost immediately and rise rapidly to almost seven times current levels. That would mean 2.6 million immigrants arriving each year. And Canada's population would explode to 57 million within 15 years.

Needless to say, that's impossible. Not to mention absurd -- because there's no way we could boost numbers that high.

Canadians like to think that most of the planet is covered by teeming masses of poor people in hopeless countries. Billions upon billions of them. And every single one of those people would sell a kidney to come to Canada, drive a cab, and shiver for six months of the year.

In the past, that satisfying image bore some resemblance to reality. Today, it increasingly does not. In a few decades, it's likely that Canadians will be amazed to recall we once thought that way.

Country after country has gone through, or is going through, or will soon go through, two transitions. There's a demographic transition from high fertility and high mortality to low fertility and mortality. And there's a development transition --from a poor, rural and agricultural society to a wealthier, urban, and industrial (or post-industrial) society.

Before countries undergo these transitions, they have lots of people who would happily drive a cab in Canada or some other rich country. But after? Drive your own cab, foreigner. They're staying home.

It has happened time after time. For centuries, Ireland's biggest export was people but today Ireland is a net importer. Italy overflowed with babies only a couple of generations ago but Italy's fertility rate has been so low for so long the population will soon start to decline.

This isn't a Western thing. China and India are well into their demographic and industrial transitions. We still think of them as almost limitless sources of poor, young, hardworking people who would be delighted to come here and start at the bottom of the ladder. But that is changing fast. Mexico. Turkey. Vietnam. South Korea. The details vary but the general direction is the same all over the world. Even among the 50 poorest nations on the planet, fertility rates are falling -- the United Nations expects them to plummet from 4.6 babies per woman today to 2.5 in 2045.

The same UN projection shows world population growth ceasing around 2050.

All these means that a rapidly growing number of countries is competing to attract a rapidly shrinking number of skilled immigrants: We may loosen the tap on immigration one day and find that nothing comes out.

If that day comes, you can be sure we will wish we had had more babies.