In Praise of the Danish Mortgage System

When interest rates go up, the price of bonds goes down. As Tyler and I discuss in Modern Principles, the inverse relationship between interest rates and prices holds for any asset that pays out over time. In particular, as Patrick McKenzie points out, when interest rates go up, the value of a loan goes down. McKenzie suggests that you can use this fact to buy back your mortgage from a bank when interest rates rise.

For example, suppose you get a 500k 30-year fixed rate mortgage when interest rates are 3%–that loan obligates you to pay $2108 per month for 30 years. Now suppose that interest rates go to 6%, now that same stream of payments is only worth, in present value, about $358k. Thus, the bank should be willing to let you buy your mortgage for $358k–that is, after all, what the market would pay for such a stream of payments if your mortgage was securitized.

I am skeptical that I could find the right person at the right bank to actually authorize a deal like this but it turns out that the Danish mortgage system is built to allow this relatively easily. The Danish mortgage system is built on the match principle:

JYSKE Bank: The match-funding principle entails that for every loan made by the mortgage bank, a new bond is issued with matching cash-flow properties. This eliminates mismatches in cash-flows and refinancing risk for the mortgage bank, which also secures payments for the bondholder. In the Danish mortgage system the mortgage bank functions as an intermediary between the investor and borrower. Mortgage banks fund loans on a current basis, meaning that the bond must be sold before the loan can be given. This also entails that the market price of the bond determines the loan rate. The loan is therefore equal to the investment, which passes through the mortgage bank.

In essence, in the Danish system, mortgage banks are more like a futures clearinghouse or a platform (ala Airbnb) than a lender–they take on some credit risk but not interest rate risk.

Thus, if a Danish borrower takes out a 500k mortgage at 3% interest and then rates rise to 6%, the value of that mortgage falls to $358k and the borrower could go to the market, buy their own mortgage, deliver it to the bank, and, in this way, extinguish the loan. Since the value of homes also falls as interest rates rise this is also a neat bit of insurance. Remarkable!

The Danish mortgage market appears to be very successful and so may be a model for American reform:

JYSKE Bank: The Danish Mortgage Bond Market is one of the oldest and most stable in the world, tracing its roots all the way back to 1797 with no records of defaults since inception. Furthermore, the market value of the Danish Mortgage Bond Market is approx. EUR 402bn, making it the largest mortgage bond market in Europe.


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