Financial assets across the world have taken a beating since the start of the year. Policymakers in emerging markets already know the feeling. Since the long boom in middle-income economies came to an end two or three years ago and waves of turbulence rocked their asset markets, central banks and finance ministries have been trying to work out what to do.

自今年开始以来，全球金融资产受到了重创。新兴市场的政策制定者此前就已体会到这种感觉。自从两三年前中等收入经济体的长期繁荣走向终结、其资本市场受到多轮动荡冲击以来，这些经济体的央行和财长一直在试图想出应对之策。

Investors still too often treat emerging economies as though they were an undifferentiated mass. In reality some have more options than others, depending on how policymakers prepared for the inevitable tightening of external financial conditions.

太多时候，投资者仍将各新兴市场经济体视为互无差别的一个群体。事实上，其中一些经济体面临的选择比其他经济体多一些，具体要看各个经济体的政策制定者为不可避免的外部资金状况收紧做准备的情况如何。

One of the more original contributions to the debate arrived this week from Agustín Carstens, the well-regarded governor of the Banco de Mexico. He suggested central banks look to intervene in bond markets to prevent a credit crunch. The withdrawal of foreign capital has starved many emerging market sovereign debt markets of a ready supply of buyers.

受到业界敬重的墨西哥央行(Banco de México)行长阿古斯丁愠斯滕斯(Agustín Carstens,上图)本周为这场辩论贡献了一个更具原创性的点子。他建议各央行寻求干预债券市场，以阻止一场信贷紧缩。外国资本的撤出，令许多新兴市场主权债务市场缺乏现成的买方。

Mr Carstens stopped short of advocating full-blown quantitative easing on the model of the US Federal Reserve and other developed economy central banks. Instead, he suggested that central banks could swap long-dated bonds for short-dated, thus easing liquidity problems further down the yield curve and in effect acting as a market-maker of last resort.

卡斯滕斯终究没有呼吁按照美国美联储(Fed)及其他发达经济体央行的模式、推行大规模量化宽松，而是建议各央行可以用短期债券交换长期债券，从而以较低的收益率缓解流动性问题，在实质上扮演最后做市商的角色。

For a relatively stable, functioning economy like Mexico, such a move may make sense, though it carries substantial risks. Mr Carstens accepted that it would be a policy to which he would turn only reluctantly.

对于墨西哥这样相对稳定、运转正常的经济体来说，这一举措可能是合理的——尽管它可能会带来很大风险。卡斯滕斯承认，他只会在被逼无奈的情况下实施这一政策。

For the more typical emerging market where the fiscal solvency of the government is doubtful, the dangers of such a policy almost certainly outweigh the benefits. The problem arises from the aftermath of the flood of capital into emerging markets during the boom that followed the global financial crisis. The inflow was aided, ironically enough, by the QE practised by the Fed, which sent money around the world searching for higher yields. While emerging market governments often avoided racking up big debts themselves, many of their corporates went on a dollar-denominated borrowing spree that left economies vulnerable to currency depreciation.

对于政府财政偿付能力令人怀疑的更典型的新兴市场，实施这种政策的危险几乎肯定超过了它带来的好处。这其中的问题，来自在全球金融危机后的繁荣期大量涌入新兴市场的资金的影响。足够讽刺的是，当初对新兴市场的资金流入起到推波助澜作用的正是美联储实施的量化宽松计划，该计划向全球各地输送了大量寻求更高收益的资金。尽管新兴市场政府本身大多会避免积累高额债务，但新兴市场的企业中却有不少大肆借入了以美元计价的债务，从而令新兴市场经济体易于受到本国货币贬值的冲击。

In this context, undertaking a policy that is likely to be seen as monetary loosening while the Fed is tightening is fraught with the danger of encouraging further devaluation, making the debt problem worse. This is particularly true for those economies like Brazil and South Africa, where high inflation and fiscal laxity have driven down their currencies and questioned the solvency of the government, let alone their corporates.

在这种局面下，在美联储收紧货币政策的同时，实施一种可能会被视为货币宽松政策的举措，极有可能促使本国货币进一步贬值，从而令债务问题恶化。对于巴西和南非这类经济体尤为如此：在这些经济体中，高通胀和宽松的财政政策已压低了本币汇率，令就连政府的偿债能力都受到质疑，更不用说企业的了。

Ultimately, the credibility of monetary policy needs fiscal solidity as a backstop. The policy outlined by Mr Carstens makes sense only if it involves tiding markets over a bad patch that policymakers, and investors, can safely regard as temporary. That is not, sadly, the position in which many emerging markets find themselves.

归根结底，货币政策的可信度需要财政实力做后盾。卡斯滕斯提出的政策建议，只有在一种情况下是合理的：当市场面临的糟糕状况是政策制定者和投资者能够有把握地认定为临时性的，这一政策不过是为了帮助市场渡过这一临时难关。可悲的是，许多新兴市场的处境并非如此。

It is hard to think of more than a small handful of countries where the idea of the central bank being market-maker of last resort is both practicable and reasonably safe. Emerging markets rode out the global financial crisis in 2008 and 2009 quite well relative to developed economies. They are unlikely to do so again this time.

央行充当最后做市商的想法既具备可行性又比较安全的国家寥寥无几。相对于发达经济体，新兴市场生龙活虎地渡过了2008年至2009年的全球金融危机。这一次，它们不太可能再这样。

Mr Carstens’s idea is an interesting intervention in the debate about the function of central banks in the emerging markets. Unfortunately, with the exception of himself, there appear to be few central bank governors for whom it is a wise proposition.

在这场关于新兴市场央行功能的辩论中，卡斯滕斯提出的想法是一次有趣的参与。遗憾的是，除了对他自己而言，这个提议对其他几乎所有央行行长而言似乎都是不明智的。