Let's take a quick look at how CMHC mortgage rule changes and the average house price in Saskatoon have fared over the last decade.
Here is a quick list of CMHC down payment requirements and max amortizations over the years.
1954- In 1954, the federal government expanded the National Housing Act to allow chartered banks to enter the NHA lending field. CMHC introduced Mortgage Loan Insurance, taking on mortgage risks with a 25% down payment
1954-1990- Somewhere along this time, 10% became minimum down payment.
1992- 5% was introduced as a trial run, then officially accepted in 1999.
2001 – Genworth (GE Capital) enters the Canadian mortgage insurance market
2001 – CIBC offered below-prime mortgages.
Pre-2003 – CMHC: 5% down with price limit depending on area, 25 yr amortizations, no price limit if 10% or more down
Sep 2003 – CMHC: 5% down, 25 yr amortizations, removed all price ceiling limitations. Now any mortgage would be insured regardless of the cost.
Mar 2004 – CMHC: Flex-Down product allows 5% down to be borrowed and 1.5% closing costs to be borrowed (essentially zero down, but 95% insured)
Mar 2006 – AIG enters the Canadian mortgage insurance market
Mar 2006 – CMHC: 0% down, 30 yr amortizations (Genworth announces 35 yr amortizations)
Jun 2006 – CMHC: 0% down, 35 yr amortizations, interest only payments allowed for 10 years
Nov 2006 – CMHC: 0% down, 40 yr amortizations, interest only payments allowed for 10 years
Oct 2008 – CMHC: 5% down, 35 yr amortizations, investors need 5% down.
April 2010- CMHC did some minor tightening
of their guidelines, investors need 20% down.
March 2011- CMHC only allows 30 yr amortizations, restrictions on pulling equity out
This is how mortgage rule changes and Saskatoon home sales looks like over the last few years
Here is how home sales per 10,000 people looks like over the last decade.
Here is how the mortgage rule changes and the average Saskatoon house price looks like.

While lax lending is just one of many reasons why there is a housing bubble, and lax lending is a fairly large component of the bubble, I believe even if mortgage rules were never expanded from 5% over 25 years with a price ceiling to what we have today, Canada and Saskatoon would still have a housing bubble. Not as big mind you, but what we need to understand, is what lax lending did, was amplify the housing bubble from a smaller bubble into a bigger bubble. Max amortizations of 30 years is not much more than 25 years, but I believe the biggest increase of "lax lending" was by removing the price ceiling. Add it all up and lax lending allowed marginal buyers to borrow more money and many of these buyers bought at or close to their maximum affordability and this helped push up house prices. Because of global real estate fever, it would not have mattered if it was 25 years or 40 years, buyers would still have been after "the prize" and would have borrowed to their max. The result of this is now in plain sight as almost daily we hear that " household debt in Canada is the number one domestic problem" in regards to the Canadian economy.
Household debt is near $1.6 trillion dollars, leaving Canadians with a household debt to income ratio of 153%, a household debt to GDP ratio of 94% and which both are growing. These ratios are too high for many reasons and the growth is unsustainable as many Canadians will find out the hard way. I will touch upon this in a post " why a soft landing in the Canadian housing market is highly unlikely."
While I believe more mortgage tightening is definitely needed in the Canadian housing market, to pin the problem of the housing bubble solely on CMHC is wrong. There are many other variables ( buyer psychology, low rates, the positive feedback loop with house prices, risk aversion from other asset classes, and other government policies, stimulus and subsidies) as to why the housing bubble was blown up in the first place and they are still alive and well today. But because people do not buy homes, people with mortgage buy homes, CMHC does have the power to make the housing market sustainable and affordable once again. Instituting a price ceiling like there was in 2003 would do this. Will they?