When it comes to home values, mortgage payment affordability acts like a giant lever.

A meaningful rise in mortgage payments (relative to income), would bear down on home prices, and vice versa.

Given this relationship and today’s towering home values, mortgage affordability is centre stage. That has inspired a stream of articles about whether swarms of people will default when rates “normalize.”

But how worrisome is that threat really? For insights, we turned to BMO Capital Markets Senior Economist Sal Guatieri.

To preface everything, here are some data points to consider…

…On Affordability

• According to BMO, home ownership is “affordable” (for the median buyer) when mortgage carrying costs—monthly payments, property taxes, heat, etc.—don’t exceed 39% of family income.
• Nationwide, we’re at about 31.6% today.¹

…On Mortgage Payments

• If we look specifically at mortgage payments, BMO says the average-priced house currently consumes 28% of median household income, based on non-discounted mortgage rates.²
• That puts us right at the long-term average (see chart below)
• This 28% falls to 23% for people living outside Vancouver and Toronto.
• Compare these numbers to the peaks of 44% in 1989 and 36% in 2007.

What if rates normalize?

The first step is to define “normal.” We can be reasonably confident that the new normal is less than the old normal. Reasons for that include the long-term downtrend in our domestic growth rate (see chart) and proactive inflation control by the Bank of Canada.

To pump life into the economy, the BoC has kept Canada’s overnight rate at just 1.00% for 902 straight days. According to Guatieri, “A normalized overnight rate would be closer to 3.50% given the inflation target of about 2.00%.”

This implies that short-term rates should theoretically jump by about 2.5 percentage points…someday. In turn, long-term rates (such as 5-year fixed rates) should rise less, maybe 200 basis points says Guatieri. That would push 5-year fixed mortgages somewhere near 4.99%.

Other things equal, these new “normalized” rates would drive up mortgage carrying costs (assuming 10% down) from 31.6% of gross income today to 37.2%. That would still fall below BMO’s threshold of unaffordability, which is 39%. But keep in mind, these affordability metrics don’t include other personal debt like car payments and credit cards.

How will borrowers be affected? 

RBC Economics writes, “Residential property values are elevated in Canada and, for many households, ownership remains accessible only because of rock-bottom mortgage rates.”

(Higher incomes have also helped affordability, notes BMO.)

But escalating interest rates aren’t necessarily a death knell. Reason being, “the eventual rise in rates will take place at a time when the Canadian economy is on a stronger footing, thereby generating solid household income gains,” says RBC. That, in turn, “would provide some offset to any negative effects from rising rates.”

The key word there is “some.” Guatieri estimates that, “To fully (our emphasis) offset a two percentage point increase in rates, household income would need to rise 19%, which could take six years if average income grows at the 3% average pace of the past decade.”

Incidentally, for major affordability damage to be done, we’d need something equivalent to a rate shock and/or serious unemployment. A rate shock is a fairly rapid increase in mortgage rates of “more than two percentage points,” Guatieri explains.

How far off is the threat?

It’s difficult to estimate the probability of a rate shock, Guatieri acknowledges. “The debt market is even pricing in a small probability of a BoC rate cut later this year.”

RBC notes, “We expect the Bank of Canada to leave its overnight rate unchanged at 1% throughout 2013 and raise it only gradually starting in early 2014—a scenario posing little in the way of imminent threat.”

Take that rate forecast for what it’s worth, but regardless, “affordability is not a major problem and should not become one even when rates normalize,” Guatieri writes in this report.

That’s true even in three of the fastest growing provinces—Newfoundland, Alberta and Saskatchewan.

The affordability exceptions, not surprisingly, are detached homes in Vancouver, Toronto and Victoria. Not coincidentally, these three markets are among the most prone to the one thing that helps affordability the most: a material price correction.

Footnotes:

¹ Based on a 2.99% 5-year fixed rate, property taxes equalling 1% of home value, $150 per month for heating cost, a 25-year amortization, plus fourth-quarter 2012 data provided by BMO, including: Q4 household income estimated at $75,300, an average seasonally adjusted home price of $361,523 and a down payment equalling half of personal income (i.e., $37,600 or ~10%).

² Same assumptions as above, save for the mortgage rate. BMO uses an interest rate of 4.1% for its analysis. This higher rate makes comparisons easier over the long-run, since discounts were smaller in the past and since discounted rate data from the 1980’s is scarce.

Rob McLister, CMT