全球主權債券收益率現正卡在接近歷史低點的水平，上周三德國首次發行了收益率為負的30年期國債。

雖然債券市場可能預示著全球經濟走向衰退，但各國政府越來越渴望利用借貸成本降到歷史低點的機會籌集資金，填補近乎持續的赤字。

這很可能是美國財政部為何低調提到正在嘗試推出“超長期”國債，即發行之日起50年或100年后到期的政府債券。目前，美國政府發售的國債最長期限是30年。

美國政府之所以意識到現在是重新討論“超長期”國債的好時機，創紀錄的低利率肯定是關鍵原因之一，如此一來政府就能夠鎖定未來數十年的低資本成本。但是，長期利率的下降實際上已經持續一段時間，“世紀債券”這種比人類平均壽命還要長的債券反映出至關重要的事實，那就是人口老齡化和出生率下降，在悲觀主義者看來意味著經濟逐漸僵化。

“全世界出現劇烈的人口結構變化。”在舊金山聯儲近日發布的一份研究報告中，卡洛斯·卡瓦略、安德烈·費雷羅和費爾南達·內希奧寫道。“在大多數發達經濟體中，實際壽命和預期壽命都已經穩步增加。預期壽命的增加將會拉長個人的退休時間，從而促使人們在整個生命周期中更愿意儲蓄而非消費……預期壽命的增加給利率帶來了下行壓力。”。

“債券的主要買方是企業養老金計劃和保險公司。”康橋匯世的投資組合經理亞歷克斯·尼珀說道。“尤其企業養老金正轉向對沖負債而非擴大資產基礎，所以會傾向于找期限更長的債券。”

過去幾年，包括富裕的大學和醫療保健網絡在內的少數大公司已經注意到趨勢，紛紛發行了百年債券。2014年克利夫蘭診所就已經發行了超長期債券，而賓夕法尼亞大學也在上月發行了定于2119年到期的債券，收益率為3.61%。同日，30年期美國國債的收益率約為2.5%。

這表明收益率曲線變平（意味著長期借貸的成本不會遠高于短期借貸）刺激發債方借債50年或100年，而非20年或30年。在經濟合作與發展組織的34個成員國中，已經有14個國家發行了期限從40年到100年不等的主權債券。而且隨著歐元區借貸成本的下降，過去兩年奧地利、比利時和愛爾蘭紛紛發行了百年債券。值得注意的是，發行方大多是人口增長放緩且國民壽命增長的國家。

美國財政部在8月20日的提議并不是第一次有意推出超長期債券，早在上一次金融危機過后，奧巴馬政府就提出并討論過這個問題，而在2017年，現任財政部部長史蒂文·姆努欽也曾經提出過相同想法。

今年早些時候，美國財政部甚至提出了發行永久債券的想法，永久債券沒有到期日，但會永遠支付利息（中世紀時期大多數債券均是如此運作，但情況并不一樣）。

不過，就在30年期國債收益率史上首次跌破2%的當天，美國財政部決定嘗試發行超長期國債，這無疑讓市場觀察人士吃了一驚。

“這不是美國財政部的常規做法，比較出人意料，選擇在8月中旬流動性較低的周五下午，還跳出了兩周半以前剛剛發布的季度舊債換新指引。”美銀美林的美國利率策略主管馬克·卡巴納說道。“我們不確定美國財政部發布該聲明的原因，但可能反映政府希望利用處在歷史低位的長期利率，抵抗收益率曲線倒掛造成的經濟衰退憂慮。”

然而，看起來銀行界對該想法似乎熱情不大。

“之前美國財政部多次研究過發行長期國債的問題，每次結論都是不符合納稅人的最佳利益。” 卡巴納補充道。“2017年研究時，他們發現沒有證據表明市場對期限超過30年的國債存在強勁或是可持續的需求。我們認為，財政部本輪試探也不會得出什么新結論。”

美國財政部網站顯示，下屬的債務管理辦公室正在就超長期債券“聯系市場，以了解市場對超長債券的最新看法”，咨詢完成后再決定是否采取行動。（財富中文網）

譯者：艾倫

審校：夏林

Sovereign bond yields across the globe are stuck nearall-time historic lows, with Germany issuing negatively-yielding 30-year debtfor the first time ever on last Wednesday.

While bond markets may be signalling recession ahead for the global economy, governments around the world are increasingly eager to take advantage of historic low borrowing costs to fund their near continuous deficits.

That’s likely one reason why the US Treasury quietly mentioned last Friday that it was putting out feelers for “ultra-long” Treasury bonds—meaning government debt that would mature 50 or 100 years from the date of issuance. Currently, the longest maturity of sovereign debt that the US government sells is 30 years.

Record low interest rates are certainly a crucial reason why the US government sees an opportunity to reopen the conversation around ultra-long bonds, given the opportunity to lock in a low cost of capital for decades to come. But considering that long-term interest rates have actually been falling for some time now, “century bonds” or debt dated longer than the average human lifespan crucially reflects how our populations are aging, our birth rates declining, and to pessimists, our economies ossifying.

“The world is undergoing a dramatic demographic transition,” wrote Carlos Carvalho, Andrea Ferrero, and Fernanda Nechio in a recent research piece for the Federal Reserve Bank of San Francisco. “In most advanced economies, actual and expected longevity have increased steadily. An increase in life expectancy would lengthen individuals’ retirement period, generating additional incentives to save rather than spend throughout the life cycle… and increase in life expectancy puts downward pressure on rates.”

“The primary consumer of these bonds would be corporate pension plans and insurance companies,” said Alex Nepper, portfolio manager at Cambridge Associates. “Corporate pensions in particular have shifting towards hedging their liabilities overtime as opposed to growing their asset base, so they would look for longer-dated debt.”

A handful of large companies including wealthy universities and health care networks have already caught on and issued century-long debt in the past years. Among many others, that includes the Cleveland Clinic in 2014and most recently the University of Pennsylvania, which last month issued abond that matures in 2119 and yields 3.61%. On the same day, US Treasury bondsdated 30 years yielded around 2.5%.

That goes to show how a flat yield curve (meaning it doesn’t cost much more to borrow for longer periods of time) incentivizes borrowing for 50 or 100 years rather than 20 or 30 years. Already, fourteen countries inside the 34-country strong OECD have issued sovereign debt with maturities ranging from 40 to 100 years, and Austria, Belgium, and Ireland have all issued century-bonds within the past two years as Eurozone borrowing costs have declined. Notably, these countries are predominately made up of countries with slowing population growth and increasing lifespans.

August 20’s proposals were not the first time that the US government has toyed with the idea of ultra-long bond. After the financial crisis they were put up for discussion by the Obama Administration, and they were reproposed in 2017 under Treasury Secretary Steven Mnuchin.

Earlier this year the Treasury Department even tabled the idea of issuing perpetual bonds. That is, bonds that never mature but pay interest into eternity (the way most bonds worked around the Middle Ages, but that’s another story).

Still it definitely took market watchers by surprise when news on a new exploration of ultra-long issuance broke on the same day that after the 30-year yield fell below 2% for the first time ever.

“This is a surprising break from typical Treasury practice since it was unexpected, late on a mid-August Friday in low liquidity, and outside of quarterly refunding guidance that was just provided 2.5 weeks earlier,” said Mark Cabana, CFA, heads of US rates strategy at Bank of AmericaMerrill Lynch. “We are not sure why Treasury delivered such an announcement but expect it reflects a desire to take advantage of historically low long-dated interest rates, and push back on recession concerns from an inverted yield curve.”

However, there doesn’t appear to all that much enthusiasm within the banking community about the idea this time around, either.

“Treasury has studied ultra issuance numerous times in the past and has always concluded it was not in the best interest of the taxpayer,”Cabana added. “In their 2017 study, they did not see evidence of strong or sustainable demand for maturities beyond 30 years. We doubt Treasury's conclusions from upcoming outreach will be materially different.”

Per the US Treasury’s website, the Treasury’s Office of Debt Management is currently conducting “market outreach to refresh its understanding of market appetite” for ultra-long debt and will take a decision whether to proceed following that consultation.