美国贸易逆差和外债：还能持续多久？

Tamim Bayoumiisa visiting scholar atKing’s College.Joseph E. Gagnonis seniorfellow at the PetersonInstitute for InternationalEconomics. INTRODUCTION AND SUMMARYOn April 2, 2025, President Donald Trump announced the largest tariff increasein US history, with effective tariffs calculated to rise from 2.5 percent to22.5 percent.1The purpose of the tariffs is to eliminate the chronic US tradedeficit based on a mercantilist view that surplus countries are winners and deficitcountries are losers from trade. Leaving aside the fraught question of whethertariffs will reduce the deficit, this paper asks why US trade has been in deficit forso long and explores the economic risks and consequences posed by the massiveforeign borrowing that years of deficits have engendered.US external accounts have been in deficit for almost half a century, and theseimbalances have recently grown. Since 2019, the US current account (CA) deficithas roughly doubled, the goods and services (trade) deficit has increased, andreported US net liabilities to the rest of the world reached an unprecedented90 percent of GDP.2Despite this deterioration in external sustainability, academicand policy-oriented economists have had little to say. This paper shows that theUnited States was on a sustainable path prior to the COVID-19 pandemic, despitemoderately large external deficits. US net liabilities looked set to stabilize around50 percent of GDP (the growth of net liabilities since the pandemic largely reflectsthe boom in US equity markets and measurement error). However, the recent rise indeficits is not a measurement error and is not likely sustainable. Indeed, we estimatethat a significant but not unprecedented decrease in the trade deficit of 2 percentof GDP is needed to make it sustainable. Moreover, if the United States were to loseits ability to borrow at a very low rate of interest, the required adjustment couldalmost double, making sustainability much more difficult to achieve.Two previous expansions of US external deficits (in the early 1980s and mid-2000s) attracted considerable attention among economists and in the popularpress. This paper reviews the academic literature around the 2006 postwarpeak of the US CA deficit at 6 percent of GDP.3There was broad agreementthat a deficit of such a magnitude was not likely to be sustainable, but therewas less consensus on the risks and costs that might be associated with afuture adjustment.The Great Recession of 2008–09 brought about a sharp depreciation inthe dollar and reduction in US external deficits, but most observers do notattribute a large role to the external deficits or their adjustment in causing thedownturn. Rather, lax US financial supervision, poor lending standards, andunderappreciated risks in new structured financial assets are generally viewedas the proximate causes of the recession. Thus, it appears that trade adjustmentwas a relatively low-cost byproduct of a domestic financial crisis by reducing therelative attractiveness of US assets for international investors.1Seehttps://budgetlab.yale.edu/research/where-we-stand-fiscal-economic-and-distributional-effects-all-us-tariffs-enacted-2025-through-april.2The current account is the broadest measure of the external balance, including all receipts fromand payments to foreigners. In principle, the CA balance determines net borrowing from (or netliabilities to) the rest of the world. The goods and services balance is commonly referred to byeconomists as the trade balance, and most of the movements in the CA balance are driven bythe trade balance. Together, we refer to them as the external balances. Some observers and theTrump administration call the goods balance the “trade” balance, but we do not examine thegoods balance in this paper because there is no economic reason to exclude trade in services.3The earlier peak reflected an overvaluation of the dollar that was reversed through coordinatedpolicy action under the auspices of the Plaza Agreement. From 2013 through 2019, the US CA deficit was relatively stable, around2 percent of GDP. Although the dollar began to appreciate in late 2014, thisappreciation did not widen the deficit because it was associated with a sharpdrop in US energy imports owing to the domestic fracking revolution. A 2 percentdeficit would be expected to stabilize US net international liabilities around50 percent of GDP. Although large by US historical standards, other advancedeconomies had experienced even higher ratios of net liabilities to GDP (Australia,New Zealand, Spain).The COVID-19 pandemic in 2020 brought sharp temporary swings in theexternal balances and exchange rates followed by persistently stronger growthin the United States than in its trading partners, mainly fueled by loose fiscalpolicy and a bullish attitude to the US technology sector, which pushed thedollar up even further. The result has been a widening of the CA deficit to around4 percent of GDP and a massive increase in the reported US net