Hyun Song Shin, who is on leave from Princeton while chief economist at the Bank for International Settlements in Basel, spends a lot of time wondering what could cause the next financial crisis. He suspects it will be something different from the leveraged bets on housing that were at the root of the last crisis.

So, what might it be? Perhaps the steady rise of the U.S. dollar on global currency markets.

In recent presentations at the Brookings Institution, Mr. Shin documented the growing use of the U.S. dollar by borrowers and lenders outside of this country. U.S. banks and bond investors have lent $2.3 trillion outside the U.S. Foreign banks and foreign bond investors have lent much more: $6.5 trillion.