在过去六个月里，日元对美元贬值约9%，对欧元则跌至单一货币27年来最弱水平，同时10年期国债收益率升至约1.8%，30年期收益率攀升至3.3%，为1999年推出长债以来最高。新任首相高市早苗推出规模17.7万亿日元（约1130亿美元）的补充预算，虽然占GDP比例不大，却在更高通胀和更高收益率环境下加剧市场对财政扩张的担忧。

日本当前面临“收益率上升、货币贬值”的组合，这种情形过去多见于新兴市场，如今在发达经济体中也出现，类似2022年特拉斯短暂执政期间英国金边债收益率飙升、英镑暴跌，以及今年投资者抛售美国国债和美元的情形。由于政府债务规模庞大，即便收益率小幅上升也会显著推高利息支出，尽管今年预算赤字约为GDP的1.3%，明显低于英国和美国。

约3%的通胀帮助日本将政府净债务从五年前的GDP约162%降至约130%，但以削弱居民尤其是低收入和固定收入群体的实际购买力为代价，而且这一改善难以为继；IMF预计到2030年赤字将升至约GDP的4.4%，远高于预期增速。若出现更持久的抛售并引发资本外流，可能迫使日本央行更大幅度加息，并促使财务省动用约1.3万亿美元外汇储备干预汇市。

Over the past six months, the yen has fallen about 9% against the dollar and hit its weakest level ever against the euro, while ten‑year Japanese government bond yields have risen to roughly 1.8% and 30‑year yields to 3.3%, the highest since long bonds were introduced in 1999. Prime Minister Sanae Takaichi’s supplementary budget of ¥17.7 trillion (about $113 billion), although small as a share of GDP, heightens concerns about fiscal expansion in an environment of higher inflation and higher yields.

Japan now faces the “yields up, currency down” pattern once associated mainly with emerging markets, a dynamic that has also appeared in rich countries such as Britain during Liz Truss’s brief premiership and, more recently, in U.S. Treasuries and the dollar. Because Japan’s government debt stock is enormous, even modest increases in yields sharply lift interest costs, though this year’s budget deficit is only about 1.3% of GDP, far below those of Britain and America.

Inflation of around 3% has helped reduce net government debt from roughly 162% of GDP five years ago to about 130% today, but at the cost of eroding consumers’ purchasing power, especially for low and fixed incomes, and this improvement is unlikely to last as the IMF projects the deficit to widen to about 4.4% of GDP by 2030. A deeper sell‑off and potential capital flight could eventually force the Bank of Japan to raise rates more decisively and push the finance ministry to deploy part of Japan’s $1.3 trillion in foreign‑exchange reserves to defend the yen.