Why did the ridings change?

The Constitution includes a formula for deciding how many seats each province gets in the House. Part of that formula is population-based, so riding boundaries get redrawn every decade based on the latest census data about how many Canadians there are and where they live. Each province has its own independent commission that decides, with some input from the public, where the ridings’ boundaries should go. (Those boundaries never change in the territories, though, as each one is a single riding.)

Where are these 30 new ridings?

The seat counts have increased in four provinces. The biggest gains were in Western Canada and the Greater Toronto Area, regions with rapid population growth.

While Saskatchewan’s seat count stayed the same, it dramatically shifted the boundaries of its 14 ridings, carving out new urban seats in Regina and Saskatoon.

But wait, some provinces gained lots of new seats and mine didn’t gain any. Is that fair?

When they designed our parliamentary system in the 19th century, the Fathers of Confederation ensured that representation by population – the principle that more populous areas should get more say in government – would decide the makeup of the House. (Full disclosure: One of the biggest cheerleaders for rep-by-pop was George Brown, the founder of this newspaper.) But there were provisos, checks and balances to make sure bigger and faster-growing provinces didn’t dominate the smaller ones.

The Senate, for instance (whose seat count is based on regions, not population) was designed to give smaller provinces a counterweight in Parliament. The government also tinkered with the House’s seat-count formula over the decades as new provinces joined Confederation and their populations grew or shrank. Sometimes provinces lose seats, though the current rules make sure seat counts don’t fall below certain levels.

Could these new ridings decide the election’s outcome?

Possibly. Last year, Elections Canada took the 2011 election results, broke the votes down by neighbourhood and plugged them into the 2015 ridings, to see which parties would benefit most. Their analysis found that, if Canadians voted the same way today as they did in 2011, the Conservatives would win 22 more seats, with six more seats for the New Democratic Party and two more for the Liberals.

The Conservatives would have taken all of Alberta’s new seats, most of B.C.’s and some of Ontario’s too. The NDP would have had a slight advantage in Saskatchewan’s new urban ridings, which used to be part of mixed urban-rural ridings that had voted Conservative: Elections Canada’s analysis found the NDP would have won two of the urban Saskatchewan seats.

No one can tell for sure how the parties will fare in the new ridings until election day. In the meantime, though, you can check our election forecasting tool to see who’s ahead in the polls and project who’s likely to win.