当下世界经济面临较为重要的转折点，次贷危机以来泛滥的流动性引致资产价格高企，金融行业膨胀。尽管美中经济增长有所回稳，但随着主要央行加息缩表，首当其冲的可能并非增长能否稳定，而是资产泡沫的回撤能否有序。而仰视屡创历史新高的美国股市，不免让人心生恐惧。

奥巴马扩张。美国当下的社会经济现状很大程度上是以奥巴马为标志的左倾理念的产物。就摆脱次贷危机的成本而言，从2008年至今，美国GDP从14.7万亿美元扩张到目前的19万亿美元，增长约30%，但美联储的资产负债规模则从不足1万亿美元扩张到4.5万亿美元，联邦债务从10万亿美元扩张到19万亿美元。如此急剧的财政货币刺激，换得了今日美国经济增长、就业和通胀的大致正常。但2.5%左右的经济增长率仍明显低于美国经济长期增长趋势线，而美国地产、股市和债市则处于历史高点。宏观调控刺激剧烈，经济增长平稳平庸，资产价格却高不可攀。

特朗普拐弯。很明显，奥巴马的治理思路难以持续，因此特朗普在诸多领域的政策主张都呈现出明显的拐弯特征。比较中国对4万亿元刺激及之后的“三期叠加”，特朗普拐弯也呈现出对货币和财政政策的明显调整姿态。如何评价奥巴马政治遗产也许仍有待时日，而特朗普新政则命运多舛，不过，对明显不可持续的政策进行修正很可能是必要的。大致稳定的增长和16年来最好的就业状况，给拐弯提供了契机。

美国股市泡沫。围绕美国股市是否存在泡沫的争论，从2015年延续至今，美股在争论中不断高攀，在特朗普当选之后则重新明确了向上升势，股市给出了特朗普溢价。就美国楼市而言，情况尚好，过去十年累计房价上涨超过30%的有10个州，超过10%的则有25个州，并不过分。就美国债市而言，如果美联储持续加息节奏不减，那么到2018年底，短期利率有可能比2016年底翻倍，达到2%左右，债市压力沉重。但最令人担忧的可能还是美国股市，当下美国股市市值超过GDP的2倍，历史上达到该比率时，美国都发生了严重股灾，例如2001年的科技股泡沫和2008年的次贷泡沫。当下美股市盈率和市净率分别为22倍和3.6倍，处于较高估值的75%分位。这比A股估值几乎贵了1倍，而A股则处于历史较低估值的25%分位，同时A股和H股之间的价差也处于历史低位。

纳斯达克尤其让人心怀恐惧。当下纳斯达克估值超过33倍，其市值占美国股市总市值的比例也在历史高位，市盈率超百倍的公司比比皆是。次贷危机至今，道琼斯上升了3倍，而纳斯达克指数则上升了5倍。同期美国经济仅增长了30%。看起来，一些现象级的企业都面临现形时分。例如优步（Uber），如果将其做为出租车行业的可比或备选公司来进行估值也许是合理的，但当下它却与美国前三大航空公司的总市值差不多，这就太搞笑了。不仅如此，这些估值上已属巨无霸的企业，离现金流平衡或盈亏平衡点还有距离，还需要私募投资人持续烧钱。那么，还有更多的钱可烧吗？

主要央行缩表。美联储主席耶伦近期已明确表达了缩表意愿，估计在卸任之前，她可能触及缩表举措一到两次。美联储历史上有过五六次缩表，缩表的大致结果都是增长放缓，股市下挫，利率上升和物价下行。考虑到次贷至今，美联储资负表扩张了几乎5倍，缩表至少30%也许是美联储在今后必须面对的初步目标。令人瞩目的是中国央行，次贷危机至今，中国GDP从33万亿增至约70万亿，M2余额从不足50万亿翻了3倍至突破150万亿，中央和地方财政负债也有增长。因此从2015年以来，中国央行资负表扩张规模也在不断放缓，在当下货币和监管双紧背景下，中国央行即便不太可能整体缩表，也会明显放缓流动性扩张的节奏至个位数。大致可以说，全球流动性面临着次贷危机以来的十年拐点，中国流动性则面临着改革开放以来30年的拐点。这种流动性长期拐点的出现，不可能不对资产价格，尤其是股市楼市构成持续压力。

金融地产泡沫过大。平稳平庸的实体经济，日益无法承受过去十年膨胀过度的金融和地产。而纳斯达克泡沫则是其中最为岌岌可危的。危机来了，流动性泛滥了，人们慌不择路地将大量资金投入了科技创新领域，冷落平淡无奇的传统产业。危机走了，加息缩表了，人们恍然发现，科技创新如此昂贵和充满泡沫。

总之，仰望自20世纪90年代“新经济”以来最长最猛的美国牛市，尤其是纳斯达克，我心怀恐惧。

At the present, the world economy is facing a crucial turning point. The liquidity injection has been very high since the subprime crisis. Thus, the asset price has increased and the financial market has expanded. Although US and Chinese economic growth have been stable, the main issue now is whether the asset bubble can vanish in good order rather than whether the growth will be stable with the main central banks raising interest rates and narrowing the balance sheet. A look at the record levels of the US share market can be frightening.

Obama implemented an expansion policy. The present economic situation in the US is the product of the left-wing ideas represented by Obama. In terms of the cost of getting rid of the subprime crisis, from 2008 to the present, the US GDP grew to the current $19 trillion from $14.7 trillion, up by about 30%. But the Federal Reserve asset liabilities swelled from less than $1 trillion to $4.5 trillion and the Federal debt expanded from $10 trillion to $19 trillion. This drastic fiscal and monetary stimulation brought about today's American economy. Now, the US economic growth, employment and inflation are basically normal, though its 2.5% or so economic growth is clearly lower than the long-term growth trend of the US economy. However, the US property market, share market and debt market are at an all-time high. The macro regulation gave a drastic stimulation; the economy grew steadily and the asset price was extremely high.

Trump makes changes. Obviously, it is difficult to maintain Obama's administrative policy. Thus, Trump has clearly shown his attitude to change policies in many areas. In comparison with China's four trillion yuan stimulus and the subsequent circumstances of “dealing simultaneously with the slowdown in economic growth, making difficult structural adjustment, and absorbing the effects of the previous economic stimulus policies”, Trump also tends to adjust monetary and fiscal policies. Still, it will take some time to evaluate Obama's political heritage. Trump's new policies do not go smoothly. But it is necessary to revise the unsustainable polices. The generally stable growth and the best employment situation in 16 years provide opportunities for making changes.

The US share market is bubbling. Experts have debated whether a bubble exists in the US share market since 2015, and the US share market continues to highlight the debate. The share market again showed an increasing tendency after Trump was elected. The US property market is good. Over the past 10 years, the cumulative housing price increased more than 30% in 10 states and more than 10% in 25 states. As to the US debt, if the Federal Reserve continues to increase interest rates, the short-term rate may reach 2% or so by the end of 2018, doubling the short-term rate by the end of 2016. The debt market is under a heavy burden. But the US share market could be worrisome. Now the US share market value is more than twice GDP. Historically, when the ratio between GDP and the market value was as high as this, a catastrophe would occur in the share market. The tech stock bubble in 2001 and the subprime bubble in 2008 are the two cases in point. At the present, the US share market profit rate and market rate are 22 times and 3.6 times respectively, in the 75% position of the higher valuation. It nearly doubles the A share valuation, which stays in the 25% position of the lower valuation in history. At the same time, the difference between the A share and H share is at a low historical level.

NASDAQ is particularly frightening. At the moment, the Price-to-Earning Ratio of NASDAQ exceeds 33; its market value in the total US share market value is also at a high historical level with many companies' price earnings ratio over a hundred times. Since the subprime crisis, Douglas index has tripled while the NASDAQ index is up by a factor of five. Meanwhile, the US economy only rose by 30% over the same period. It is time to cast out the phenomenal enterprises. Take Uber for example. It may be reasonable to use Uber as a comparable or alternative company to make evaluation in the taxi industry. But it is ridiculous that Uber's market value is close to the US' three top airline companies. In addition, these highly evaluated companies cannot reach cash-flow balance and breakeven point. They still need investors to keep investing. However, will there be more investors?

Main central banks tends to narrow their balance sheets. Recently, Federal Reserve chief Janet Yellen expressed the idea of narrowing the balance sheet. Presumably, Yellen could take the step of narrowing balance sheet one or twice before she leaves office. The Fed has narrowed the balance sheet five or six times. The consequence of narrowing the balance sheet was the economic slowdown, the share market slump, interest rate rise and price fall. Since the subprime crisis, the Fed Reserve has expanded the balance sheet five times. Narrowing the balance sheet by 30% at least may be the preliminary target of the Fed Reserve in the future.Take a look at China's central bank. Since the subprime crisis, China's GDP grew from 33 trillion yuan to about 70 trillion yuan; M2 balance tripled to 150 trillion yuan from less than 50 trillion yuan, and the central government and the local governments' debts also expanded. Since 2015, China's central bank has kept slowing down expansion of the balance sheet. With monetary and regulatory tightening, even if China's central bank is unlikely to narrow the entire balance sheet, it will obviously slow down the liquidity expansion to single digits. Roughly speaking, global liquidity faces a turning point nearly 10 years in the wake of subprime crisis, while China faces a turning point after 30 years' reform and opening up. These long-term turning points will create persistent pressure on asset price, especially on the share market and the property market.

The bubbles in both finance and property grow too big. The ordinary real economy is increasingly unable to bear the finance and property that over-expanded in the past ten years. And NASDAQ is the most precarious bubble among them. When a crisis comes, liquidity explodes and people invest large amount of funds into science and technology innovation in a hurry, ignoring the mundane traditional industries. When a crisis is gone and the balance sheet is narrowed, people suddenly find that the science and technology innovation is so expensive and so foamy.

All in all, watching at the American bull market, NASDAQ in particular, that has been the longest and strongest since the “New Economy” in 1990's, I feel frightened.