Writing for the National Bureau of Economic Research, Oscar Jorda, Moritz Schularick and Alan Taylor examine bubbles in housing and equity markets over the past 140 years. The most dangerous, they conclude, are housing bubbles fuelled by credit booms. The least troublesome are equity bubbles that do not rely on debt. Five years after the bursting of a debt-laden housing bubble, the authors find, GDP per person is nearly 8% lower than after a “normal” recession (ie, one that is not accompanied by a financial crisis). In contrast, five years after a stockmarket crash, GDP per person is only 1% or so lower. If the stock bubble comes alongside a big rise in debt, the damage to GDP per person is 4%. The paper does not explain why housing bubbles are more costly, but a fair inference is that, whereas equity investments tend to be concentrated among the rich, plenty of people lower down the income ladder have wealth tied up in housing.

　　在为美国国家经济研究局撰写论文中，Oscar Jorda，Moritz Schularick和Alan Taylor检验了过去140年房屋和股票市场的泡沫。他们的结论是，最危险的是由信贷繁荣带来的房产泡沫，表现最好的是不依赖借债的股票泡沫。他们发现，债务累累的房屋泡沫破裂五年后，人均GDP比“正常的”经济衰退(比如不伴随着金融危机的衰退)后要低将近8% 。相较而言，股市崩盘五年后，人均GDP只下跌1%左右。如果股市泡沫同债务上升一同发生，人均GDP则要损失4%。该论文没有解释为什么房市泡沫代价最昂贵，但是合理的推论是，股票投资更加集中于富人中间，收入较低的人们大多将财富捆绑在房屋上。

　　That makes sense. Stockmarket routs typically harm the economy via the “wealth effect”. When people see that their assets are worth substantially less than before, they spend less, leading to weaker demand and, ultimately, weaker investment. Debt can make this worse. Those who have borrowed to invest may be forced to sell assets to avoid defaulting, further depressing prices and wealth. Banks that have lent to investors or accepted shares as collateral will also suffer losses. That forces them to rein in their lending, harming the economy even more.

　　这很有道理。股市崩盘主要通过“财富效应”损害经济。当人们看到自己资产大幅缩水后，他们花费得就少了，需求也随之减少，最终投资减少。债务却能使其雪上加霜。贷款投资的人可能被迫出卖资产以避免违约，这更进一步得压低了价格和财富。给投资者贷款或者接受股票作为抵押物的银行也会蒙受损失。于是银行不得不拉紧钱袋，这会让经济遭受更大的损害。

　　In a paper for the Centre for Economic Policy Research, Markus Brunnermeier and Isabel Schnabel take an even longer view, examining 400 years of asset-price bubbles. Be it tulips, land, housing, derivatives or shares, they find that the consequences of a bursting bubble depend less on the type of asset than on how it is financed. High leverage is the telltale sign of trouble.

　　在为美国国家经济研究局的经济政策研究的论文中，Markus Brunnermeier和Isabel Schnabel看得更长远，他们检验了过去四百年的资产价格泡沫。他们发现，无论是郁金香、土地、房产、金融衍生品还是股票的泡沫，破碎后的结果更多取决于融资方式而不是资产类型。资产负债率高是问题的明显特征。

　　What does this mean for central banks? Before the financial crisis, the debate boiled down to “leaning versus cleaning”. Activist sorts argued that the monetary guardians should lean against the wind by raising interest rates when asset bubbles grew. The opposing camp, exemplified by Mr Greenspan, countered that it was too difficult to spot bubbles in advance and too costly to tighten monetary policy erroneously, so it was best to wait for them to burst before cutting rates to help clean up the mess.

　　这对央行意味着什么?金融危机前，讨论的核心是“逆势操作还是泡沫破碎后的清扫”。激进派认为货币监控者在泡沫膨胀的时候应当加息逆行操作。而以格林斯潘为代表的反对派则认为提前鉴别泡沫过于困难，若错误地收紧货币政策则后果严重，所以最好在泡沫破裂后再降息清理残局。

　　fuel: cause… to burn more intensely 助长、激化。这个词在作文中可以轻松运用：由第三次工业革命带来的科技创新 technology innovation fuelled by the Third Industrial Revolution; 由手机组件的成本降低而扩大了手机普及率 the growing popularity of cellphone fuelled by the lower cost of its parts. 由于电脑知识的普及而导致的互联网繁荣 The internet boom fuelled by the widespread computer knowledge。

　　the bursting of a bubble: 泡沫的破碎。如今“泡沫”这个词在经济学里非常火热，房产泡沫 housing bubble, 股市泡沫 stockmarket bubble, 信贷泡沫 credit bubble。

　　debt-laden: 非常生动形象的“负债累累”一词。laden表示布满…， 我们可以活用这个词：他的评论意味深长 His comments were laden with deep meaning;油脂多多的一餐 a fat-laden meal; 烟雾缭绕 smoke-laden air; 以科技装备的军队 technology-laden military.

　　lower down the income ladder: 收入阶层低一点的，说法很形象，会为作文加分哦。社会底层的人 people lower down the social ladder; The social ladder is like Mount Everest: Lots of people try to climb, but few reach the top.

　　Wealth effect：就像文中解释的一样，是人们对于财富的信心最终影响花费习惯。人们看到自己在股市中的钱大幅缩水后，认为自己不如以前富有，便开始节省开支，不愿消费，其实人们投在股市里的钱即使增值，他们也很可能用来继续投资，而不是消费，但是因为信心更足，人们消费开始放宽松，进一步刺激经济增长，这就是财富效应。如果你在某篇作文里需要用“刺激经济增长的最重要一步是让国民有信心”，那么你可以用上Wealth effect来impress考官。

　　depress: 压制 depress prices and wealth，反义词 encourage, spur, stimulate。刺激经济一揽子方案 stimulus package。

　　high leverage: leverage 杠杆效应、企业负债率，即企业的负债以期望企业的效益超出借债的成本。如果企业负债率高，最终权益效益低于借债的成本，那企业面临着高风险。

　　telltale sign：顾名思义就是一眼能看出来的信号。

　　boil down to: 归根结底，归结于。在作文开头，我们有时需要解析一下作文考题，指出考题的根本含义是什么，就可以用这个词组。The debate of “should rich countries pay more for environmental damage” boiled down to the argument if rich countries should carry more responsibilities.

　　tighten monetary policy: 收紧货币政策;放宽货币政策： loosen monetary policy