By Steve Keen
背景知識：Steve Keen，澳大利亞西悉尼大學的副教授，經濟穩定研究中心的創始人。主要研究非常規經濟理論“金融不穩定假說”，這一假說是由美國經濟學家Hyman Minsky提出。假說強調了私人債務在經濟發展中的重要性，這被主導的新古典主義經濟學派所忽視。Steve Keen在2005年的12月份就意識到私人債務/GDP比率在不斷的升高，一場嚴重的經濟危機即將發生。
“我讓Steve不定時的把他有關於債務增長對全球經濟威脅方面的文章發給我。”
~ Colin Twiggs
我的經濟學研究方法和主流的理論（“新古典主義”經濟學）的主要不同之處在於，我把貸款研究的重點放在一個動態的、不均衡的框架中。我從這個角度研究債務/GDP比率，並把該比率的變化看作反映國家經濟的關鍵因素。而正是在2005年後期警示我一場全球性的經融危機即將發生。該比率在澳大利亞和美國（我只能得到這兩個國家可靠的數據）呈現出一個清晰的指數路徑，我知道這種關系必然會打破並會對經濟造成巨大破壞。
這種現象並沒有引起傳統經濟學家足夠的重視，這也是為什麼經濟危機出乎他們意料的原因。即使在經濟危機發生之時，他們仍然沒有正確的認識債務/GDP比率的重要性，同時，他們也沒有預見經濟危機的持續性。一些傳統的經濟學家批評我把研究重點放在他們所謂的“原始”債務/GDP比率上面；另一些人則宣稱我把存量和流量相比較是在犯一個“小學生的”錯誤。為了證明債務/GDP比率的重要性，我列舉了下面的計算方法：
• 假設一個國家的名義GDP為1萬億，每年以10%的速度增長（實際產出增長5%，通貨膨脹增長5%）。
• 同時，這個國家的私人債務是1.25萬億，並以每年20%的速度增長。那麼，私人債務每年將增加0.25萬億。
• 忽略政府在財政赤字情況下的支出，那麼這個國家一年的支出（所有支出，包括投資和商品市場的支出），是1.25萬億。其中，80%為GDP收入，另外20%的支出來源於債務融資。
• 一年之後，該國的GDP收入增長10%，達到1.1萬億。
• 第二年該國的私人債務為1.5萬億（1.25萬億的20%增幅）。
• 該國的總支出為1.1萬億，這將抵消全部的GDP收入，不需要進行債務融資。
• 相比去年，今年的總支出少了0.15萬億。
• 在債務增幅不變的情況下，名義需求減少了12%。
如果第二年的債務水平實際增長並不穩定，而是和GDP一樣的增幅呢？那麼將出現以下情況：
• 第一年的總需求量是1.25萬億，包含1萬億的GDP收入和0.25萬億債務。
• 第二年，總需求仍然是1.25萬億，包括1.1萬億的GDP收入和0.15萬億的債務。
• 名義總需求量維持不變
• 但是如果考慮通貨膨脹的話，那麼實際上，名義總需求量有5%的減少。
這是由債務所帶來的真正的危險：一旦債務成為GDP的重要部分，且增幅遠超於GDP，那麼經濟將會衰退，即使債務/GDP的比率穩定。
這種方法不僅解釋了為什麼全球金融危機是不可避免的，而且對以前發生的危機也給出了一個全新的解釋。這也是為什麼迄今為止澳大利亞沒有爆發全球性的經濟危機，而美國受經濟危機影響最嚴重。
下圖顯示的是過去65年中，澳大利亞債務/GDP比率的年度變化。藍色表示保守、自由黨贏得選舉權，黑色表示激進的工黨（ALP， The Australian Labor Party）贏得選舉權，而綠色表示工黨沖破萬難贏得選舉權。請註意，在1945和1965年期間，債務/GDP比率時漲時落，在接下來的10年間，該比率一直在升高，繼而在1973年中期7%迅速回落到1975年中期的3%。，這導致了70年代中期的經濟衰退。
1988年後期至1993年早期，重複上面的模式——債務/GDP比率從7%的年增長率下降到3.5%，這促成了澳大利亞總理保羅•基廷所說的：“無法避免的經濟衰退”
就我們現在的經濟危機比以往任何一次都嚴重，不是因為債務增長更加迅速（實際上，20世紀70年代的債務增長速度比現在要高很多），而是因為現在的債務/GDP比率非常高，在2008年達到了11.5%，而2009年中期下降到-5%。
但請註意，2009年中期以後，債務/GDP比率又迅速的升高：盡管澳大利亞在20世紀90年代的經濟衰退期，債務/GDP比率下降達到33個月，但這次，比率下降僅維持了短短的13個月。
此次該比率迅速升高是受到首次購房者的推動（我本人更傾向於認為是房地產供應商的推動）。政府為每位購房者提供從7，000至1，400澳元不等的補助，該政策促使250，000的澳大利亞人利用槓桿貸款買房，繼而導致了房價升高，每套房直接給房地產供應商帶來了30至50，000美金的額外收入。
供應商又用這些增加的收入擴大投資，在政府的刺激政策之前，抵押貸款預期下降3%，而現在卻使得GDP增幅達6%——增幅9%就相當於為GDP總值為1.25萬億的國家提供了0.1萬億的資金支持。
抵押貸款的槓桿化帶來的急劇增幅超過經濟部門去槓桿化帶來的增幅，而且政府部門的債務融資也促進了債務的增長，使得需求水平達到1996至2006年水平，債務/GDP比率增長到5%，有力的促進了經濟的發展。
所以，澳大利亞一直在創造機會，努力的避免自己陷入全球經濟危機。雖然說這不完全是一件好事：為了以後能面對更大的痛苦，我們在不斷的避免痛苦。而美國，正在經歷著最為嚴重的全球經濟危機因為它正試圖通過去槓桿化來減少貸款，從而降低債務/GDP比率。盡管過程很痛苦，但是至少觸及到了危機的根源——過高的債務。
相對與澳大利亞，美國更像是一個龐氏騙局的主導者。減少私人借貸——現在龐氏騙局已經識破——是美國經濟衰退的主要原因。下圖顯示的是增加的債務需求和債務融資之間的關系——該關系我認為是債務的變化/(GDP總量+債務變化)。債務的變化使得需求從20%下降到5%。只有政府大規模的增加貸款才能減少去槓桿化的影響。
政府的支出是否能夠繼續對抗私人借貸的去槓桿化是一個争議的話題。我的一些非主流經濟學同事認為政府的財政赤字可以促進國家的經濟繁榮。盡管我質疑他們的說法，但毫無疑問的是，如果“赤字鷹派”促使政府減少支出，那麼就沒有力量可以阻止私人貸款的去槓桿化。
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.
文章翻譯由兄弟財經提供，
本文來源：http://www.incrediblecharts.com/economy/keen_debt_gdp.php