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 investors 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 premier, 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 speculation, reforms to the markets and a stockmarket slump 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-earnings 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 structural reform ongoing, 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' propensity to save is not matched by investment options. Capital controls stop money going abroad; bank deposits are unattractive b