紧缩还是不紧缩——在这个问题上，政策制定者已开始了改变自己的答案。他们这么做是否正确？这是英国《金融时报》本周探讨的议题，就像是上世纪30年代激烈讨论的重演。如果支持紧缩的论点是正确的，那么不实行紧缩，就会给一些全球最重要的国家带来财政和金融冲击。如果支持紧缩的论点是错误的，那么决定紧缩就会危及复苏，可能还会触发进一步的财政危机。

政策制定者怎么想？20国集团(G20)多伦多峰会闭幕后发表的宣言称：“在多个主要经济体中同步的财政调整可能对复苏造成负面影响。在必要时未能加固复苏可能会破坏信心且阻碍增长。考虑到这一平衡，发达经济体已承诺在2013年之前将赤字减半，并在2016年之前降低政府负债与国内生产总值(GDP)的比率。”

上述辞令明显比2009年9月匹兹堡峰会的宣言更谨慎。匹兹堡宣言大胆地宣称：“我们今天承诺，在经济实现持久复苏之前，将维持有力的政策应对措施。我们将采取行动，确保在恢复增长的同时，就业也能恢复增长。我们将避免过早退出刺激政策。与此同时，我们将着手准备退出策略，在时机合适的时候，以协调合作的方式，撤回我们异乎寻常的政策支持，信守我们对财政责任的承诺。”

那么，哪些情况发生了改变？

第一个答案是：世界经济复苏的势头比预期更为强劲。在2009年4月G20伦敦峰会召开之际，人们普遍预测2010年全球经济增速为1.9%。到去年9月，这一数字已上调至2.6%，到今年6月则为3.5%。对于美国的经济增速，去年4月、去年9月和今年6月的普遍预测分别为1.8%、2.4%和3.3%。即便是对欧元区，普遍预测数据也略有上调，从去年4月的0.3%，至去年9月的1%，再到今年6月的1.1%。

第二个答案取决于希腊及其它欧元区外围成员国的财政危机，英国联合政府的当选又加剧了危机。投资者避险情绪高涨：今年5月，希腊10年期债券收益率达到逾12%的峰值。这导致国际货币基金组织(IMF)及其它欧元区成员国政府联手出台了一项救助方案，并创建了一项7500亿欧元的IMF/欧元区联合稳定机制。

紧缩的力度也不能过分夸大。经合组织(OECD)在5月份的《经济展望》(Economic Outlook)中预测，2011年，整个组织经周期性调整后的财政赤字将从2010年的6.4%降至5.8%。美国的相应数据分别为9%和7.9%，欧元区为4.1%和3.6%。但目前各国都在计划进一步紧缩，尤其是英国。此外，许多人认为，拟议中财政紧缩的力度还不够。

那么，各方都有何理由呢？

反对赤字的一派认为，财政赤字对经济活动没有任何影响，因为它们会导致私人做出抵消性的行为。因此，如果政府实行赤字财政，私人就会储蓄，因为他们明白自己的税负最终会上涨。截然相反的一派认为，深度衰退将清除以往的过剩，由此让经济和社会更健康。尽管那些想法如此极端的人影响着广泛的政治领域，但他们对政策制定者的直接影响却有限。那么，政策制定者辩论的焦点是什么？

最后，如果在财政紧缩后经济有所衰落，放松银根会非常有效。通过鼓励投资和降低汇率（因此也包括促进出口），就能让后者发挥作用。许多主张削减赤字的人还表示，最好的应对措施是削减支出。他们称，这是从以往的财政紧缩中汲取的教训。

主张推迟紧缩的人同意，必须果断放缓长期支出的增长。但他们强调，复苏仍然非常脆弱，尤其是私人部门仍拥有庞大的财务盈余。他们坚持认为，这种私人部门的节俭造成了财政赤字，而不是反过来。从事件发生的先后顺序就可以清楚地看出这一点。

主张推迟者补充表示，我们还看到了投资者的大规模避险：对于恐慌的投资者而言，他们别无选择，只能逃向高评级政府的债券，尤其是全球安全港货币发行国——美国的债券。由于欧元区危机，美元的这一地位已变得更加牢固。此外，主要国家的长期利率在不断下降，而非上升：在美国，10年期国债收益率为3%。那么，对信心的威胁在哪里呢？

此外，主张推迟者还会说，由于利率接近于零，除了能支持财政放松，货币政策没有什么效果。幸运的是，拥有央行的国家能直接为财政赤字提供融资。欧元区成员国就做不到这一点，因为它们实际上使用的是一种外币。只要产能过剩情况仍然如此严重，正常的银行放贷仍然如此疲弱，这种对央行“印钞机”的依赖就不会带来通胀风险。相反，毋宁说危险在于过早实行财政紧缩会导致经济急剧减速，就像上世纪90年代的日本一样，由此将重要的经济体拖入通缩。

他们指出，高负债与通缩相互作用，会造成螺旋式下降。日本式“失落的十年”威胁着整个发达世界。如果每个人都勒紧腰带，这种情况就尤其可能发生。如果是这样，那就有必要进一步实行财政放松：今年一季度，七国集团(G7)所有成员国的GDP仍低于危机前的最高水平。

对于本周辩论各方论点的是非曲直，读者们必须自己拿主意。我本人强烈支持推迟紧缩。但有一点是所有人都认可的，即这场辩论很重要。我们无法确定谁是对的，但我们可以确定，如果政策制定者走错了路，结果可能会很严重。医生们必须做好准备，要对自己所偏爱疗法的不良反应迅速拿出应对措施。

WHY THE BATTLE IS JOINED OVER TIGHTENING

To tighten or not to tighten – that is the question. It is one to which policymakers have started changing their answers. Are they right to do so? That is the issue addressed in the Financial Times this week, echoing the fierce debates of the 1930s. If arguments for tightening are correct, failure to do so would bring fiscal and financial shocks in some of the world's most important countries. If arguments for tightening are false, decisions to do so threaten recovery and might trigger further financial shocks.

Where are the policymakers? The declaration after the Toronto summit of the Group of 20 leading nations, stated: “There is a risk that synchronised fiscal adjustment across several major economies could adversely impact the recovery. There is also a risk that the failure to implement consolidation where necessary would undermine confidence and hamper growth. Reflecting this balance, advanced economies have committed to fiscal plans that will at least halve deficits by 2013 and stabilise or reduce government debt-to-gross domestic product ratios by 2016.”

This language is notably more cautious than that of the Pittsburgh summit of September 2009. That stated boldly: “We pledge today to sustain our strong policy response until a durable recovery is secured. We will act to ensure that when growth returns, jobs do too. We will avoid any premature withdrawal of stimulus. At the same time, we will prepare our exit strategies and, when the time is right, withdraw our extraordinary policy support in a co-operative and co-ordinated way, maintaining our commitment to fiscal responsibility.”

So what has changed?

The first answer is that the world economy is recovering more strongly than expected. In April 2009, at the time of the London G20 summit, the consensus of forecasts for global economic growth this year was 1.9 per cent. By last September it had reached 2.6 per cent. By June 2010, it was 3.5 per cent. In the US, the consensus forecasts for 2010 were 1.8 per cent in April 2009, 2.4 per cent last September and 3.3 per cent in June 2010. Even for the eurozone, the consensus of forecasts has moved a little, from 0.3 per cent in April 2009, to 1 per cent last September and 1.1 per cent in June 2010.

The second answer lies with the fiscal crises in Greece and other peripheral members of the eurozone, reinforced by the election of the coalition government in the UK. The flight from risk was dramatic: in May, the yield on Greek 10-year bonds peaked at more than 12 per cent. This led to a rescue package by the International Monetary Fund and other eurozone governments, and the creation of a new €750bn joint IMF and eurozone stabilisation facility.

The extent of the tightening must also not be exaggerated. In its May Economic Outlook, the Organisation for Economic Co-operation and Development forecast a decline in cyclically adjusted fiscal deficits for the grouping as a whole from 6.4 per cent in 2010 to 5.8 per cent in 2011. Corresponding figures were 9 per cent and 7.9 per cent for the US, and 4.1 per cent and 3.6 per cent for the eurozone. But further tightening is now planned, particularly in the UK. Moreover, many think planned fiscal tightening does not go far enough.

What, then, are the arguments?

The “cutters” argue that such huge fiscal deficits – never seen in peacetime in big developed countries, notably the US – threaten long-term fiscal credibility and depress private confidence and spending. While piling fiscal stimulus on top of the built-in stabilisers made sense in the panic of 2008 and early 2009, the time has come for swift consolidation. Otherwise, a spike in borrowing costs looms, with dire results. The permanent loss of output and revenue left behind by the crisis, along with ageing populations, make action inescapable and urgent.

Finally, should economies weaken after a fiscal tightening, monetary loosening would be highly effective. The latter can work by encouraging investment and weakening exchange rates, so also encouraging exports. Many cutters also argue that the best response would be to reduce spending. That is the lesson, they say, from past fiscal retrenchment.

The “postponers” agree there must be decisive slowing of the growth of long-term spending. But they emphasise the fragility of recovery and, in particular, the huge private sector financial surpluses. This private frugality has caused the fiscal deficits, they insist, not the other way round. The sequence of events makes that evident.

Moreover, add postponers, we have seen a strong flight to safety: for the panickers, there is no alternative to bonds of highly rated governments, particularly the US, issuer of the world's safe-haven currency. Since the eurozone crisis, that role has become more entrenched. Moreover, the long-term interest rates of leading countries are falling, not rising: in the US, 10-year Treasury bond rates are 3 per cent. Where, then, is the threat to confidence?

Moreover, postponers would add, with interest rates close to zero, monetary policy is ineffective, except to the extent that it supports fiscal loosening. Fortunately, countries with their own central banks can finance fiscal deficits directly. This is untrue for members of the eurozone, which are, in effect, operating with a foreign currency. So long as excess capacity remains so large and normal bank lending so weak, such reliance on the central bank “printing press” creates no inflationary danger. On the contrary, the danger is rather that premature fiscal tightening would trigger a sharp economic slowdown, as in Japan in the 1990s, so pitching important economies into deflation.

The interaction of high indebtedness with deflation could, they argue, create a downward spiral. A Japanese-style “lost decade” threatens the developed world. That is particularly likely if everybody tightens together. If anything, further loosening is needed: in the first quarter of 2010, the GDP of every member of the Group of Seven leading countries was still below its pre-crisis peak.

Readers must make up their own minds on the merits of the arguments this week. My own strong sympathies are with the postponers. But on one thing everybody agrees: this debate matters. We cannot be sure who is right. But we can be sure that, if policymakers get it wrong, the results may well be dire. Physicians must prepare to respond swiftly to adverse reactions to their favoured course of treatment.