投資者因擔心通膨高於目標及財政赤字難以控制，日益要求長天期政府債券提供更高的溢價。本週 30 年期美國公債殖利率升至 5.33%，創 2007 年以來新高；法國借貸成本觸及 2008 年以來最高點，德國公債則交投於 2011 年水準。英國同等公債殖利率也正逼近 6%。

儘管債市尚未定價危機且短期債務相對平穩（如美國 2 年期殖利率過去一個月幾乎未動，且 MSCI 世界股票指數接近新高），但 30 年期美國公債價格下跌正迫使資產配置者重新思考投資組合。隨著長天期公債失去避險標籤，對美國債務水準的疑慮也隨之升溫。

Yardeni Research 指出，市場越來越擔憂超大規模企業借貸激增，並質疑若油價上漲，聯準會是否能對通膨保持足夠警覺。儘管殖利率上升反映後全球金融危機時代的結束，但若殖利率如 2023 年夏季般從 4% 飆升至 5%，未來或許會出現類似的買進機會，後續發展仍有待觀察。

Investors are increasingly demanding a higher premium for long-dated government bonds due to concerns over above-target inflation and uncontrollable fiscal deficits. This week, the yield on 30-year US Treasuries rose to 5.33%, the highest since 2007. French borrowing costs reached their highest point since 2008, and German peers traded at 2011 levels. Equivalent UK gilt yields are approaching 6%.

Although the bond market is not yet pricing in a crisis and short-term debt remains relatively stable (e.g., the US two-year yield has barely moved in the past month, and the MSCI world equity index is near a record high), the tumble in 30-year US bond prices is forcing asset allocators to rethink portfolio mixes. As long-dated Treasuries lose their haven tag, doubts over US debt levels are rising.

Yardeni Research noted that the market is becoming more concerned about the surge in borrowing by hyperscalers and questioning whether the Federal Reserve will remain sufficiently vigilant on inflation if oil prices climb. While the increase in yields reinforces the passing of the post-global financial era, if yields surge from 4% to 5% as they did in the summer of 2023, there may be a similar buying opportunity ahead, and future developments remain crucial to watch.