The conventional explanation is that they saw a last chance to bring attention to their plight and put pressure on the Chinese government, just as it tries to showcase the "new China" through the Beijing Olympics. Possible, but not certain: since the opening of relations with China in the 70's, no Western government has cared much about Tibet, and none is likely to damage its relations with China because of a riot in Lhassa.

There is another, hypothetical but intriguing, explanation: that the Tibetans have sensed some uncertainty and wavering in the Beijing government, possibly a slippage in its control over the country, and tried their luck, hoping their example would spread.

That the massive Chinese communist apparatus would lose control over its people might appear impossible at first. Yet Chinese history is replete with massive collapses. Huge and desperate popular uprisings could in fact be called a Chinese specialty, as they brought to an end a number of Chinese dynasties, including the last one. Is there a likelihood of this happening again?

China today is widely admired for its extraordinary economic growth, which is the result of a coherent policy. After Mao's death the rulers of China saw their socialist country falling ever further behind the West in terms of economic growth and technical capability. They concluded that this disadvantage could only be overcome with a massive infusion of money and technology from Western nations.

To achieve this, the (still very communist) rulers of China created an export-oriented capitalist sector within their command economy. The foundation of this sector was to be the "China price", or manufacturing costs so low that corporations the world over would bring their manufacturing operations to China, providing the capital and know-how. The low costs were based primarily on China's vast pool of underemployed rural labor, but other factors contributed as well: the pre-existing social safety nets were dismantled; environmental protections remained purely theoretical; capital cost was kept low, and various export subsidies were put in place; work safety rules, if any, were ignored; land for new facilities could be expropriated cheaply, and resources such as water and energy were provided at cost, if not below.

The result was the "Chinese economic miracle", with growth rates of 10% or so a year. The price was heavy: a growing income gap between rich and poor, universal corruption, severe misallocation of capital and catastrophic environmental degradation. It was assumed, however, that such a price could be tolerated as long as the economy kept expanding and the standard of living improved, at least minimally, for all. So far the policy has worked.

But there was a catch or two. For one, China has become increasingly dependent on the rise of private consumption in the developed world, and has become vulnerable to the capitalist economic cycle of growth and recession, boom and bust, a cycle it cannot control. Second, the phenomenal growth of the Chinese export economy has generated enormous demand for resources, including energy, raw materials and agricultural commodities. The resulting inflationary spike has been proportional to the demand, particularly in the food sector, on which the Chinese spend a third of their income. Inflation is rapidly eroding the improvement in living standards brought by the economic boom.

At the same time a US recession would put a major dent in Chinese growth, producing unemployment and reducing the economic compensation for the ills that unchecked development has brought. It is hard to gage the public mood in a country where information is tightly controlled, but there is one potential indicator: the Shanghai stock market, which, unlike the one in Hong-Kong, is open to Chinese only (no foreigners).

Because all assets in China are still owned and/or controlled by the government, there are few opportunities to invest. The internal stock market was one, and millions of investors have bought into it. The result was a remarkable rise in market value. But in November of last year the market peaked, and has since lost roughly 40% of its peak value.

That could well be just another financial bubble popping. But it could also say a lot about the people's confidence in China's future.