Gian Maria Milesi-Ferretti, a senior fellow in the Hutchins Center on Fiscal & Monetary Policy and a former deputy director in the research department of the International Monetary Fund, has long studied the flow of money across national borders and the relationship between countries that borrow a lot from other countries and those that lend or invest a lot in other countries. His latest work examines the large gap between the total amount of reported cross-border liabilities (essentially sums that residents of one country owe residents of others) and cross-border assets (investments, such as stocks and bonds, that residents of one country have in others). Here is a Q&A with him about this project.