中国股市或许还不是一个泡沫。不过，当中国官员开始提到"泡沫"一词时，正如中国全国人大(NPC)副委员长成思危在昨日接受访谈时那样，投资者就应该小心了。

China probably does not have a stockmarket bubble yet. But when Chinese officials start to use the B-word - as Cheng Siwei, vice-chairman of the National People's Congress, did yesterday - it is time for investors¹ to worry.

2001年3月，时任中国总理的朱镕基警告称，中国B股市场出现泡沫是"无法避免的"。那一场泡沫或许无法避免，但它也没有持久。其后，中国政府开始严厉打击非法利用银行贷款进行股市投机的行为，并对股市展开改革，而中国股市随即也陷入了长达5年的熊市。

In March 2001, Zhu Rongji, then China's premier², warned that a bubble in the country's B-shares was "un-avoidable". It may have been unavoid-able but it was also unsustainable. There followed a crackdown on illegal bank loans used for speculation³, reforms to the markets and a stockmarket slump⁴ that lasted for five years.

历史似乎正在重演，尤其是在面向国内投资者的中国A股市场上。上海A股指数去年上涨了138%，而今年以来的上涨速度还在不断加快，一些股票的市盈率已经高达40或50倍。

Now history seems to be repeating itself, especially in China's A-share market, which is reserved for domestic investors. The Shanghai A-Share index went up by 138 per cent last year, rising at an ever faster pace as the year went on, with price-to-earnings⁵ multiples for some stocks reaching 40 or 50.

股市涨速快、估值高，本身并不意味着泡沫。但是，当投资者购买股票的理由，并非他们认为其拥有良好的价值，而仅仅是因为它们的价格正在上涨，在这种情况下，股市就会产生泡沫。如果投资者认为所有人都会采取同样做法，这可能是理性的。但是，当资产价格最终脱离它们的内在价值，同时没有新买家出现时，泡沫就会破裂。

A fast-rising and highly valued stockmarket does not, in itself, imply a bubble. A bubble occurs when investors buy stocks, not because they believe shares are good value, but simply because their prices are rising. This can be rational behaviour if investors think that everyone else will do the same. But in the end the value of assets moves out of line with their fundamental worth, the supply of new buyers runs out and the bubble bursts.

麻烦的是，投资者购买股票的原因是不可知的。或许是他们期望未来会获得丰厚收益。由于中国的经济增长率维持在每年10%左右，加之结构改革仍在推进，这并非一个高得离谱的期望。中国股市的估值确实偏高，但尚未达到离谱的程度。

The trouble is that it is impossible to know why investors are buying. It may be that they expect strong earnings in the future. In China, with economic growth around 10 per cent a year and structural⁶ reform ongoing⁷, that is not an outlandish expectation. Valuations are high, but not yet ridiculous.

问题在于，中国居民的储蓄倾向与投资选项并不匹配。资本管制使得资金难以流向国外；由于利率很低，银行存款也缺乏吸引力。与此同时，国有成分依然在国民经济中占有非常大的比例，使得中国的居民储蓄只有一个去向：股市。当股市开始上涨时，所有人都蜂拥而至。

The problem is that Chinese citizens' propensity⁸ to save is not matched by investment options. Capital controls stop money going abroad; bank deposits are unattractive because of low interest rates. The government, meanwhile, still owns a large slice of the economy, leaving China's savings⁹ only one place to go: the stockmarket. When it starts to go up, everybody piles in.

因此，尽管中国股市或许还算不上泡沫，但却可能很容易膨胀。幸运的是，与2001年相比，政府和私营部门现在可以采取很多措施，在初期就将泡沫消除。

So while China's market may not be a bubble yet, one could easily inflate¹⁰. Fortunately, compared with 2001, there is a lot the government and the private sector¹¹ can do to pop a bubble early.

这些不同措施都围绕着一个主题：增加股票供应量，以满足需求。在海外上市的企业可以回归上海或深圳市场，利用内地股市的高估值进行融资。例如，在香港和纽约上市的中国移动(China Mobile)，目前尚未回归内地股市。

These actions are variations on a theme: supply more shares to meet demand. Companies floated abroad could list in Shanghai or Shenzhen to take advantage of high valuations. Shares in China Mobile, the cellphone company, trade in Hong Kong and New York but not yet in China.

中国政府可以抓住这个机会，将更多奄奄一息的国有企业私有化。此举将深化中国金融市场，提高经济效率，同时为居民储蓄资金提供投资渠道。中国甚至可以将A股和B股市场合并。人民币实际汇率被低估的根本性问题并不会因此得到解决（这是导致投资过度和消费不足的原因），但这将是一个开端。

The government can take the opportunity to privatise more moribund¹² state companies. That would deepen China's financial markets, increase economic efficiency and give savers somewhere to put their cash. China could even unite the A and B share markets. The fundamental problem - an undervalued real exchange rate that leads to excessive investment and not enough consumption - would not be solved. But it would be a start.