As financial decisions go,
borrowing several times your annual earnings to buy a risky asset is a pretty big one.
Yet, for many people, taking out a mortgage to buy a house is something of a no-brainer.
It generally involves less agonising than, say,
how much to save for retirement or how to split your pot between cash, stocks and bonds.
One reason is that, some short-lived slumps aside,
house prices across the rich world have been buoyant since the 1950s.
More important, you need to live somewhere.
Until you own a place,
you have a natural short position in property
because you need to inhabit one for the rest of your life,
whether you rent or eventually buy.
Short positions are risky.
Who knows how far rents and prices might rise?
Buying a home closes the position, resulting in a neutral one.
Unlike other investments, it is not really a bet on where prices are headed.
The mortgage is an unfortunate necessity for those who lack the cash to buy outright,
rather than a deliberate punt on the future path of interest rates.
Thinking about a mortgage as a component in the borrower's investment portfolio might therefore seem odd.
It should not.