Justin Trudeau's new cabinet might not be an accurate representation of the country, but it does reflect the Liberal caucus that Canadians sent to Ottawa last month — including the remarkably large number of Liberal MPs from the two provinces that kept the party in power.

That MPs from Ontario and Quebec are taking up a lot of space around the cabinet table is no surprise, but it does mean that these two provinces now have more clout in cabinet than they've enjoyed in decades.

Three-quarters of cabinet members — including the prime minister — represent ridings in Ontario or Quebec, which is far more than these two provinces' share of the national population. Ontario leads the way with 17 ministers or 46 per cent of the cabinet roster, followed by Quebec with 11 ministers (including Trudeau), or 30 per cent.

British Columbia and Atlantic Canada each sent four ministers to cabinet, giving them each 11 per cent of the total and putting their cabinet representation roughly on par with their national share of the population.

With just one minister from Manitoba, however, the three Prairie provinces occupy only three per cent of the cabinet seats — roughly a sixth of their national share of the population.

Regional distribution is just one of the principles that prime ministers take into account when assembling a cabinet. Maintaining that regional distribution — an aspect of government that's as old as Confederation itself — ensures that a variety of viewpoints are represented at the cabinet table and no part of the country feels particularly slighted.

But regional distribution is heavily dependent on the material available to a prime minister. Trudeau has many MPs from Ontario and Quebec to choose from — 73 per cent of his caucus members come from these two provinces.

The Liberals elected no MPs in Alberta or Saskatchewan and just four in Manitoba. There are as many Prince Edward Islanders in the Liberal caucus as there are MPs from the Prairies.

Assuming he was unwilling to appoint a minister from outside caucus, Trudeau's options were limited. Still, the current roster represents a departure from most cabinet appointments in the past.

The most Ontario, Quebec ministers in years

While the representation of B.C. and Atlantic Canada in the cabinet is fairly typical by historical standards, that's not the case for other parts of the country.

Taking into account only the initial post-election cabinet appointments (the ones prime ministers draw up as their 'ideal' cabinets, before bad performances, scandals and departures force them to make changes), Quebec now has the most representation around the cabinet table it's seen since Brian Mulroney's first cabinet following the 1988 election.

For Ontario, you have to go back to 1965 to find a post-election cabinet with as large a share of Ontario ministers as this one. That 1965 cabinet also was the last one to see such a low level of representation from the Prairies (Lester Pearson's Liberals won a single seat in the region).

Regional representation in Justin Trudeau's cabinet appointed Nov. 20, 2019. (CBC News)

This is a significant shift for the Prairies. With the sole exception of Paul Martin's post-election cabinet in 2004, Prairie ministers have made up at least 11 per cent of every post-election cabinet since 1984 — topping out at about a quarter of cabinet during the Stephen Harper years.

It also reverses a negative trend line for Quebec. Since the mid-1970s, Quebec ministers have taken up less and less space around the cabinet table. Fewer than a third of Mulroney's ministers were Quebecers. That dropped to between 20 and 25 per cent in Jean Chrétien's and Martin's post-election cabinets, and to well under 20 per cent in Harper's.

After Justin Trudeau won the most seats in Quebec in the 2015 election, the province got its fair share of seats (23 per cent) around the cabinet table — as did virtually every other region of the country.

But the Liberals no longer have that luxury — which explains the boost for both Ontario and Quebec. The regional disparity in cabinet representation looks even less proportionate when you look at the number of ministers representing ridings in the two provinces' major urban centres. Eleven ministers come from the Greater Toronto Area, while seven come from the island of Montreal — including Trudeau himself.

Throw the four B.C. ministers from Greater Vancouver into the mix and you have a cabinet mostly drawn from Canada's three largest metropolitan centres. That's also the case for the larger Liberal caucus, of course.

Central Liberal cabinets, western Conservative ones

The cabinet's tilt toward Ontario and Quebec could have been predicted based solely on which party formed government.

Since 1957, post-election cabinets formed by Liberal governments have averaged 40 per cent representation from Ontario and 29 per cent from Quebec, with only nine per cent from the Prairies. PC and Conservative post-election cabinets have averaged 22 per cent from the Prairies, with 33 per cent from Ontario and 18 per cent from Quebec.

There is no significant difference between the two parties in terms of cabinet representation from B.C. and Atlantic Canada.

So a dearth of Prairie voices in a Liberal cabinet is nothing particularly new — though the severity of it in this case is certainly unusual. The outcome of last month's election explains much of this, but not all of it. Just 22 per cent of the caucus is from Quebec — considerably less than the province's current footprint in cabinet.

It all suggests that Prime Minister Trudeau sees shoring up Quebec as key to his government's future survival, just as it was with his father in the days of 'French Power' in Ottawa. Plus ça change ...