债务与 GDP 比率的重要性

By Steve Keen

背景知识：Steve Keen，澳大利亚西悉尼大学的副教授，经济稳定研究中心的创始人。主要研究非常规经济理论“金融不稳定假说”，这一假说是由美国经济学家Hyman Minsky提出。假说强调了私人债务在经济发展中的重要性，这被主导的新古典主义经济学派所忽视。Steve Keen在2005年的12月份就意识到私人债务/GDP比率在不断的升高，一场严重的经济危机即将发生。

“我让Steve不定时的把他有关于债务增长对全球经济威胁方面的文章发给我。”
~ Colin Twiggs

我的经济学研究方法和主流的理论（“新古典主义”经济学）的主要不同之处在于，我把贷款研究的重点放在一个动态的、不均衡的框架中。我从这个角度研究债务/GDP比率，并把该比率的变化看作反映国家经济的关键因素。而正是在2005年后期警示我一场全球性的经融危机即将发生。该比率在澳大利亚和美国（我只能得到这两个国家可靠的数据）呈现出一个清晰的指数路径，我知道这种关系必然会打破并会对经济造成巨大破坏。
 
这种现象并没有引起传统经济学家足够的重视，这也是为什么经济危机出乎他们意料的原因。即使在经济危机发生之时，他们仍然没有正确的认识债务/GDP比率的重要性，同时，他们也没有预见经济危机的持续性。一些传统的经济学家批评我把研究重点放在他们所谓的“原始”债务/GDP比率上面；另一些人则宣称我把存量和流量相比较是在犯一个“小学生的”错误。为了证明债务/GDP比率的重要性，我列举了下面的计算方法：

• 假设一个国家的名义GDP为1万亿，每年以10%的速度增长（实际产出增长5%，通货膨胀增长5%）。
• 同时，这个国家的私人债务是1.25万亿，并以每年20%的速度增长。那么，私人债务每年将增加0.25万亿。
• 忽略政府在财政赤字情况下的支出，那么这个国家一年的支出（所有支出，包括投资和商品市场的支出），是1.25万亿。其中，80%为GDP收入，另外20%的支出来源于债务融资。
• 一年之后，该国的GDP收入增长10%，达到1.1万亿。
• 第二年该国的私人债务为1.5万亿（1.25万亿的20%增幅）。
• 该国的总支出为1.1万亿，这将抵消全部的GDP收入，不需要进行债务融资。
• 相比去年，今年的总支出少了0.15万亿。
• 在债务增幅不变的情况下，名义需求减少了12%。
如果第二年的债务水平实际增长并不稳定，而是和GDP一样的增幅呢？那么将出现以下情况：
• 第一年的总需求量是1.25万亿，包含1万亿的GDP收入和0.25万亿债务。
• 第二年，总需求仍然是1.25万亿，包括1.1万亿的GDP收入和0.15万亿的债务。
• 名义总需求量维持不变
• 但是如果考虑通货膨胀的话，那么实际上，名义总需求量有5%的减少。

这是由债务所带来的真正的危险：一旦债务成为GDP的重要部分，且增幅远超于GDP，那么经济将会衰退，即使债务/GDP的比率稳定。

这种方法不仅解释了为什么全球金融危机是不可避免的，而且对以前发生的危机也给出了一个全新的解释。这也是为什么迄今为止澳大利亚没有爆发全球性的经济危机，而美国受经济危机影响最严重。

下图显示的是过去65年中，澳大利亚债务/GDP比率的年度变化。蓝色表示保守、自由党赢得选举权，黑色表示激进的工党（ALP， The Australian Labor Party）赢得选举权，而绿色表示工党冲破万难赢得选举权。请注意，在1945和1965年期间，债务/GDP比率时涨时落，在接下来的10年间，该比率一直在升高，继而在1973年中期7%迅速回落到1975年中期的3%。，这导致了70年代中期的经济衰退。

1988年后期至1993年早期，重复上面的模式——债务/GDP比率从7%的年增长率下降到3.5%，这促成了澳大利亚总理保罗•基廷所说的：“无法避免的经济衰退”

就我们现在的经济危机比以往任何一次都严重，不是因为债务增长更加迅速（实际上，20世纪70年代的债务增长速度比现在要高很多），而是因为现在的债务/GDP比率非常高，在2008年达到了11.5%，而2009年中期下降到-5%。
 
但请注意，2009年中期以后，债务/GDP比率又迅速的升高：尽管澳大利亚在20世纪90年代的经济衰退期，债务/GDP比率下降达到33个月，但这次，比率下降仅维持了短短的13个月。

此次该比率迅速升高是受到首次购房者的推动（我本人更倾向于认为是房地产供应商的推动）。政府为每位购房者提供从7，000至1，400澳元不等的补助，该政策促使250，000的澳大利亚人利用杠杆贷款买房，继而导致了房价升高，每套房直接给房地产供应商带来了30至50，000美金的额外收入。

供应商又用这些增加的收入扩大投资，在政府的刺激政策之前，抵押贷款预期下降3%，而现在却使得GDP增幅达6%——增幅9%就相当于为GDP总值为1.25万亿的国家提供了0.1万亿的资金支持。

抵押贷款的杠杆化带来的急剧增幅超过经济部门去杠杆化带来的增幅，而且政府部门的债务融资也促进了债务的增长，使得需求水平达到1996至2006年水平，债务/GDP比率增长到5%，有力的促进了经济的发展。
 
所以，澳大利亚一直在创造机会，努力的避免自己陷入全球经济危机。虽然说这不完全是一件好事：为了以后能面对更大的痛苦，我们在不断的避免痛苦。而美国，正在经历着最为严重的全球经济危机因为它正试图通过去杠杆化来减少贷款，从而降低债务/GDP比率。尽管过程很痛苦，但是至少触及到了危机的根源——过高的债务。

相对与澳大利亚，美国更像是一个庞氏骗局的主导者。减少私人借贷——现在庞氏骗局已经识破——是美国经济衰退的主要原因。下图显示的是增加的债务需求和债务融资之间的关系——该关系我认为是债务的变化/(GDP总量+债务变化)。债务的变化使得需求从20%下降到5%。只有政府大规模的增加贷款才能减少去杠杆化的影响。
 
政府的支出是否能够继续对抗私人借贷的去杠杆化是一个争议的话题。我的一些非主流经济学同事认为政府的财政赤字可以促进国家的经济繁荣。尽管我质疑他们的说法，但毫无疑问的是，如果“赤字鹰派”促使政府减少支出，那么就没有力量可以阻止私人贷款的去杠杆化。

Why the Debt to GDP Ratio matters
By Steve Keen

BackgroundSteve Keen is Associate Professor at the University Of Western Sydney in Australia and founder of the Center for Economic Stability, which evolved from his blog Debtwatch. Steve is an expert in the unconventional economic theory called "The Financial Instability Hypothesis", which was developed by the American economist Hyman Minsky.

Minsky's hypothesis emphasizes the importance of private debt in the economy — something that is ignored by the dominant "neoclassical" school of economics — and Steve's awareness of the rising ratio of private debt to GDP in Australia and the US is why he predicted, as early as December 2005, that a serious financial crisis was about to occur.

I have asked Steve to submit occasional articles based on his research into the threat of burgeoning debt to the global economy.

~ Colin Twiggs

The main feature distinguishing my approach to economics from mainstream theory (known as "neoclassical" economics) is a focus upon the importance of credit in a dynamic, non-equilibrium framework. From this perspective I identify the ratio of debt to GDP — and the rate of change of that ratio — as the key determinant of the state of the economy, and this is what alerted me to the approaching Global Financial Crisis in late 2005. Debt to GDP levels in both Australia and the USA — the two countries for which I could get reliable data — were clearly on an exponential path that I knew had to break and cause a large economic breakdown.
This phenomenon was not taken seriously by conventional economists — which is why the crisis took them by surprise — and they continue to misunderstand why it matters, even as the crisis that they did not see coming continues. Some conventional economists have criticized me for focusing on what they call a "crude" private debt to GDP ratio; others allege that I am making a "schoolboy error" by comparing a stock to a flow. In response, I have developed a simple numerical example that hopefully illustrates why the debt to GDP ratio matters.
• Imagine a country with a nominal GDP of $1,000 billion, which is growing at 10% per annum (real output is growing at 5% p.a. and inflation is 5% p.a.);
• It also has an aggregate private debt level of $1,250 billion which is growing at 20% p.a., so that private debt increases by $250 billion that year;
• Ignoring for the moment the contribution from government deficit spending, total spending in that economy for that year — on all markets, including assets as well as commodities — is therefore $1,250 billion. 80% of this is financed by incomes (GDP) and 20% is financed by increased debt;
• One year later, the GDP has grown by 10% to $1,100 billion;
• Now imagine that debt stabilises at $1,500 billion, so that the change in debt that year is zero;
• Then total spending in the economy is $1,100 billion, consisting of $1.1 trillion of income-financed spending and no debt-financed spending;
• This is $150 billion less than the previous year;
• Stabilisation of debt levels thus causes a 12% fall in nominal aggregate demand.
What about if debt doesn't actually stabilise in the second year, but instead grows at the same rate as GDP? Then we get the following situation:
• In the first year, total demand is $1,250 billion, consisting of $1,000 billion in income and $250 billion in increased debt;
• In the second year, total demand is also $1,250 billion, consisting of $1,100 billion in income and $150 billion in increased debt;
• Nominal aggregate demand is therefore constant;
• But after inflation, real aggregate demand will have contracted by 5%.
This is the real danger posed by debt: once debt becomes a significant fraction of GDP, and its growth rate substantially exceeds that of GDP, the economy will suffer a recession even if the debt to GDP ratio merely stabilizes.
This approach not only explains why the GFC was inevitable, but also gives a very different explanation to preceding crises, and it explains why, to date, Australia has successfully avoided the worst of the GFC while America has suffered from it very badly.
The next chart shows the annual change in the private debt to GDP ratio in Australia, and the changes in government in the last 65 years (blue for a conservative Liberal party victory, black for a progressive ALP victory, and green for one election that the ALP won against the odds). Note that between 1945 and 1965, the ratio rose as often as fell. Then for a decade the debt ratio only rose, before then falling very sharply. Its collapse from a peak rate of growth of 7% p.a. in mid-1973 to minus 3% in mid 1975 was the real caused the mid-1970s recession.
The same pattern repeats from late 1988 till early 1993 — from a growth rate of 7% to falling at 3.5% p.a. in early 1993 — and this gave Australia what its then Prime Minister Paul Keating called "the recession we had to have".
Now to our current crisis, which has been more severe than preceding crises, not because debt was rising more quickly (in fact the rate of growth of debt in the 1970s was much higher than now), but because the debt to GDP ratio is so much higher now. The growth rate peaked at 11.5% p.a. in early 2008, only to fall to minus 5% in mid-2009.
But notice how quickly that decline in Australia's debt ratio has turned into growth once more: whereas Australia experienced 33 months of falling debt to GDP in the 1990s recession, it had only 13 months of a falling debt ratio this time.
The overwhelming reason for this rapid turnaround was the First Home Owners Boost (which I prefer to call the First Home Vendors Boost). This government policy enticed 250,000 Australians into their first mortgage by the offer of an additional A$7,000-14,000 government grant. These new buyers levered this higher deposit into a far higher loan, driving up prices which then provided the vendors from whom they purchased with an additional $30-50,000.
These vendors in turn used this windfall as additional deposits in their own levered purchases. Mortgage debt, which was on track to fall 3% as a proportion of GDP prior to The Boost, instead increased by 6% of GDP — a 9% turnaround that was equivalent to an additional $100 billion stimulus to Australia's A$1.25 trillion economy.
This dramatic turnaround in mortgage debt more than countered deleveraging by the business sector, so that private debt levels rose. On top of that, the government's own debt-financed spending returned the debt contribution to demand to the average of 1996-2006, when the debt ratio grew at roughly 5% p.a. and financed an apparent boom.
So Australia has avoided the GFC by recreating the conditions that led to it. Needless to say, this is not entirely a good thing. We are potentially avoiding pain now by setting ourselves up for greater pain in the near future.
America, on the other hand, is clearly experiencing the worst of the GFC because it is deleveraging — reducing its debt to GDP ratio. Though this is painful, it at least addresses the cause of the crisis — too much private debt — by reducing it rather than increasing it once more.
Since America is even more of a Ponzi-dominated economy than Australia, this reduction in private debt — now that the Ponzi Scheme has collapsed — is the key cause of the USA's current slump. This next chart shows the relationship between the proportion of aggregate demand which is debt financed — which I define as the change in debt, divided by the sum of GDP plus the change in debt — and unemployment. The change in private sector debt has gone from boosting aggregate demand by over 20% to reducing it by almost 15%. Only a massive increase in government debt has attenuated the deleveraging.
Whether government spending can continue to counter private sector deleveraging is now a moot point. Some of my non-orthodox economics colleagues argue that a sufficiently large government deficit can return a country to economic prosperity. While I doubt this claim, it is undeniable that if the "deficit hawks" make the government reduce its own spending, then there will be no force standing in the way of accelerated private sector deleveraging.

文章翻译由兄弟财经提供，

本文来源：http://www.incrediblecharts.com/economy/keen_debt_gdp.php