How the Original Sin of Borrowing in a Foreign Currency Can Reduce the Effectiveness of Monetary Policy for Both the Borrowing and Lending Country

Link to Wikipedia article for “Original sin (economics)”

When a central bank cuts interest rates, each type of borrower-lender relationship generates more aggregate demand because (a) the shift in of the budget constraint of the lender is matched by an equal and opposite shift out in the budget constraints of the borrower, (b) borrowers generally have higher marginal propensities to consume out of changes in effective wealth and © beyond the sum of wealth effects from (a) and (b), there is also a substitution effect leading to more spending now simply because lower interest rates make spending now cheaper relative to spending later than it was before the interest rate cut. (a) is the “principle of countervailing wealth effects” I discuss in these three posts:

  1. Even Central Bankers Need Lessons on the Transmission Mechanism for Negative Interest Rates
  2. Responding to Joseph Stiglitz on Negative Interest Rates
  3. Negative Rates and the Fiscal Theory of the Price Level

The Open Economy

I laid out the principle of countervailing wealth effects in “Even Central Bankers Need Lessons on the Transmission Mechanism for Negative Interest Rates” in order to dispute the idea that causing one’s currency to depreciate was almost the sole transmission mechanism for interest rate cuts into the negative range, so I concentrated on the case where every central bank in the world simultaneously cut its target rate by 100 basis points. But it is interesting considering the open economy case with only one central bank cutting its target rate.

First, it is important to realize that thinking about wealth and substitution effects in the way I describe above is only telling about consumption and investment. The extra net exports from the outward capital flow as funds flee the low domestic interests by going abroad is an addition to aggregate demand that goes beyond the wealth and substitution effect logic above.

See “International Finance: A Primer” for why funds going outward drive net exports up. That post also explains how the outward capital flow puts more of the domestic currency in the hands of foreigners and thereby drives down the foreign-exchange value of the domestic currency.

Small Open Economy, Net Creditor in Foreign-Denominated Assets. To see if there is any chance that the wealth and substitution effect logic can overturn the effect of increased capital outflow on aggregate demand, let’s begin by considering a small open economy that is a net creditor. To the extent that anyone in the country is investing domestically both before an interest rate cut, the usual principle of countervailing wealth effects holds since both borrower and lender are domestic. Because it is a small open economy, the rate of return on foreign assets should be affected by this monetary policy move only to the extent it induces expected exchange rate movements. If people expect any mean reversion of the exchange rate, the usual depreciation of the local currency accompanying a domestic interest rate cut might make people expect a bit of mean reversion and therefore a bit lower returns on foreign assets than before the interest rate cut. But overwhelming this effect, depreciation of the domestic currency makes any foreign assets already owned look bigger in value when totaled up in the depreciate domestic currency. Overall, there is very little room for any ambiguity about the stimulative effect of interest rates cuts for a small open economy that is a net creditor: there is the stimulus to net exports from increased capital outflow, plus a higher return on foreign assets when viewed in the domestic currency, plus the higher value of foreign assets when viewed from the perspective of the domestic currency.  

Large Open Economy, Net Creditor in Foreign Denominated Assets. Now, consider a large open economy that is a net creditor. As with any monopolist that drives down prices by producing more and selling it, a net creditor country that increases its lending abroad could theoretically reduce the rates of return it gets abroad and so make itself effectively poorer. If this were the case, one would expect to have at least some people in that country suggest that it have policies to reduce its foreign lending in order to jack up its returns on foreign assets. In the absence of any such suggestion, it seems unlikely that a country in fact would make itself significantly poorer by increasing its foreign lending from its current level.

Net Creditor in Own Currency. If a country does significant lending in its own currency, such lending is still driven by interest rates abroad relative to interest rates at home, and like the purchase of foreign-denominated assets, puts the domestic currency in the hands of foreigners, who are likely to turn around and spend those funds in increasing net exports from the domestic economy. However, with the lending in the domestic currency, exchange rate changes no longer change wealth as viewed in the domestic currency. It now becomes logically possible for a cut in interest rates to reduce spending simply because of the reduced interest income from foreigners when rates are cut.

Germany. There are three ways of thinking of the situation for Germany. One is that seeing Germany as a set of creditors within the eurozone, where the entire eurozone is seen as domestic. When taking the eurozone as the main unit of analysis, and Germany as only a part, German lending to others in the eurozone is all internal and the principle of countervailing wealth effects still applies in its main form to the eurozone as a whole. 

Second, Germany can be seen as a net creditor in its own currency. 

Third, one can view the situation as the other countries in the eurozone automatically loosening their monetary policy when Germany does. The other countries loosening their monetary policy cancels out the exchange rate effects that would otherwise make the foreign assets Germans hold in other eurozone countries look like more wealth when Germany loosens its monetary policy.

Net Debtor in Own Currency. If a country owes money on net, primarily in its own currency, then in this borrower-lender relationship, a cut in interest rates will have a positive wealth on consumption by this debtor country, enhancing the positive effects on aggregate demand from borrower-lender relationships within the country, and from the capital outflow and consequent increase in net exports induced by a rate cut.  

Small Open Economy, Net Debtor in Foreign-Denominated Obligations. This case is sometimes called “original sin.” Depreciation now makes debts look larger, which should overwhelm the effect of expected mean reversion in the exchange rate in lower the rate of return on those debts. If foreign-denominated obligations are large enough, it might even become impossible to stimulate the economy with an interest rate cut. Thus, getting into this situation is quite dangerous. Countries should put policies into place to avoid owing large amounts of money in foreign-denominated obligations. And the IMF should proactively discourage countries from committing the original sin of borrowing with foreign-denominated obligations.  

Large Open Economy, Net Debtor in Foreign-Denominated Obligations. This does not literally mean a large economy, but only one that must pay higher interest rates when it owes more and can pay lower rates when it owes less. Assuming a depreciation of the currency from a monetary loosening that reduces the rate on own-currency debt raises net exports enough that a bit of the debt begins to be paid off and the rate paid on all of the foreign-denominated debt goes down when it is rolled over, that provides a bit of an extra wealth effect in the positive direction.  


Overall, the main potential loopholes to the argument that interest rate cuts should stimulate the economy come from a country’s being a large net creditor in its own currency, or a country’s being a large net debtor in foreign-denominated obligations. In both cases, someone is borrowing in a foreign currency. Overall, having countries borrow primarily in their own currency if they do borrow is an important measure for maintaining the effectiveness of monetary policy.

Note: I am worried about the chance that I might have missed some important element of the analysis I pursue in this post. Send me a tweet (@mileskimball) if you think I got something wrong or missed something. 

Update: Olivier Wang’s reply to this post generated the follow-up post More on Original Sin and the Aggregate Demand Effects of Interest Rate Cuts: Olivier Wang and Miles Kimball.”