$15 Billion Drop In New Residential Mortgage Borrowing. . . Benjamin Tal, deputy chief economist at CIBC World Markets Inc. estimates that 50 to 60 percent of a $25 Billion decline in lending activity is directly related to the new federal government stress test for mortgage borrowers. The January 1st 2018 governments stress test for mortgage lenders requires borrowers to qualify for their mortgage payments if interest rates were 2 percentage points above the rate they negotiated with their banks.