7月下旬，美国财政部长斯科特·贝森特（Scott Bessent）动用美国外汇储备，协同日本央行在外汇市场上买入日元，以应对日元兑美元自1986年以来首次跌破163关口的贬值危机。在此轮汇率干预中，日本央行代表财务省抛售了据估计超过950亿美元的外汇储备，卖出均价约为1美元兑160日元。由于其中很大一部分美元储备是在汇率低于100日元时积累的，粗略估算表明日本政府在此次交易中实现了高达5.7万亿日元（约合360亿美元）的巨额账面利润，相比之下乔治·索罗斯在1992年英镑危机中仅获利约10亿美元（折合现值约24亿美元）。

学术研究表明，日本政府、日本央行和公共养老基金持有的海外资产总规模超过日本GDP的56%，在截至2023年的25年间实现了5.8%的年均投资回报率。与此同时，日本公共部门的负债主要表现为极低成本的日元债务，使其通过资产端与负债端的息差和汇率变动成为了全球规模最大的“套息交易”（Carry Trade）投资者。尽管日本央行进行外汇干预的初衷并非盈利而是为了熨平汇率剧烈波动以对抗通缩或控制进口通胀，但这种庞大的套息模式长期以来严重依赖于超低利率环境。

然而，随着日本核心通胀率逼近2%的官方目标，市场普遍预期日本央行将在2027年7月前加息三次。这种加息预期将使日本公共部门的借贷成本在短期内激增相当于GDP的0.75%，并随着长期债务滚动进一步推高利息支出。因此，日本央行趁日元处于历史低位时抛售美元回购日元，实质上是在以极高的兑换效率削减自身的日元负债规模。尽管本次动用的950亿美元仅清偿了公共部门不足1%的生息负债，但这为日本在利率上行周期中逐步平仓其庞大的国家套息头寸提供了关键路径。

In late July, US Treasury Secretary Scott Bessent deployed American foreign-exchange reserves alongside the Bank of Japan (BoJ) to support the yen after it weakened past ¥163 per dollar for the first time since 1986. During these recent market interventions, the BoJ, acting on behalf of Japan’s Ministry of Finance, is estimated to have sold over $95bn at roughly ¥160 per dollar. Because a significant portion of these dollar holdings was originally accumulated at exchange rates below ¥100, back-of-the-envelope calculations indicate that the Japanese government realized substantial trading profits of up to ¥5.7trn ($36bn)—dwarfing George Soros's famous $1bn gain (around $2.4bn in present value) from shorting the British pound in 1992.

Academic research shows that Japan’s combined public sector—including the government, the BoJ, and state pension funds—holds foreign assets equivalent to over 56% of national GDP, which generated an average annual return of 5.8% over the quarter-century ending in 2023. In contrast, the public sector's liabilities consist predominantly of domestic, low-yielding yen obligations, effectively positioning Japan as the world's largest carry trade investor through the yield spread between foreign assets and domestic liabilities. While the central bank's currency operations were never designed for speculative profit, but rather to mitigate macroeconomic imbalances like post-bubble deflation or imported inflation, this structural setup relied heavily on perpetually depressed interest rates.

With underlying Japanese inflation approaching the BoJ's 2% target, forecasters now anticipate three interest-rate increases by July 2027. Such policy normalization presents acute financial risks, as rate hikes could rapidly elevate borrowing costs for Japan's consolidated public sector by 0.75% of GDP before long-term liabilities are even refinanced. Consequently, intervening to sell expensive dollars and purchase deeply discounted yen allows Japan to opportunistically extinguish massive tranches of domestic yen liabilities at favorable exchange ratios. Although the recent $95bn intervention absorbed less than 1% of total interest-bearing public obligations, it represents a crucial strategic step toward gradually unwinding the world’s largest sovereign carry trade.

Source: When Japan buys yen, it unwinds a dangerous trade

Subtitle: The world’s biggest carry trader begins to exit its positio

Dateline: 8月 13, 2026 03:43 上午