There used to be a saying, 'When the US sneezes, the world catches a cold.' It's a measure of China's power in the world economy today that a shiver in Shanghai can cause panic in the world's financial centres.
Last week saw the biggest fall on the New York stock exchange since 9/11, and similar falls in stock exchanges around the world. This followed a collapse of almost 10 percent on Shanghai's stock exchange.
It's not clear what triggered the fall in Shanghai. But the knock-on effect revealed a deep-seated fear that the Chinese boom may be about to burst.
Thirty years ago China accounted for less than 1 percent of world trade. Today it is the third biggest trading nation in the world.
China's economy has grown at more than 10 percent a year for the last 15 years, making it the fastest growing economy in the world.
This explosive growth is mostly due to relatively small factories producing cheap consumer goods for export to the West.
Most of these factories are wholly or partly foreign-owned, making China's success even more dependent on Western economies.
For the US, as China's biggest export market, the success is double-edged.
Cheap Chinese imports have helped the shallow recovery in the US economy over the last ten years.
And China holds huge foreign currency reserves, mostly in US dollars, which help to fund the still-growing US trade deficit.
But the faster China grows, the more it comes into conflict with US strategic interests elsewhere in the world.
Half of China's overseas investment now goes to Latin America, which the US has traditionally regarded as its backyard. And China and the US are now in direct competition for oil and other raw materials in Africa.
China is also becoming a military rival to US ambitions in Asia.
But if the US fears China's continual rise, it also fears that its growth cannot be sustained.
As Will Hutton argues in his new book The Writing On The Wall, 'China's economic model is certain to begin to change some time in the next five to ten years. The rest of the world cannot indefinitely absorb Chinese exports growing at their current rate.'
And it's by no means certain that the Chinese economy can change direction. China's success in cheaply producing particular products won't work for all consumer products, let alone heavy industry.
China is becoming increasingly high-tech, but there are as yet no signs that it is becoming a world player in heavy industries like cars, aerospace, steel or shipbuilding.
The economic boom has brought few benefits for Chinese workers.
Industrial growth has been entirely unregulated, leading to horrific levels of water and air pollution – 16 of the 20 most polluted cities in the world are in China.
Tens of millions of workers who were employed in the old state-owned industries have lost their jobs. In large parts of the countryside peasant incomes are stagnant or falling.
Things are little better for the armies of migrant workers who keep the export industries going.
A recent Amnesty International report exposed the appalling living and working conditions they face. Many work 12-14 hours a day, seven days a week, with just one day off each month. Often they are paid months in arrears, or not at all.
Over the last two years, local governments have been forced to raise minimum wages, as the numbers of migrant workers coming from inland China have dropped.
But there have also been numerous wildcat strikes, and attempts at organising trade unions for migrant workers.
Migrant workers have also been part of some of the rural riots that have erupted in recent years.
Fuelled by land-theft, pollution or official corruption, some of these riots have seen tens of thousands of workers and peasants stand up to armed police – and win.
The human cost of the economic boom has meant that the last 15 years have seen more open protests than at any time since the 1920s.
China's boom is vulnerable both to these mass protests, and to any slowdown in the Western economies.
With a recession in the US now widely predicted, China seems likely to become even more unstable.
China and the West are like two drunks propping each other up – they can keep staggering forward for some time to come, but when one goes down, the other will follow.
Last week's panic showed the widespread fears that the tumble will come sooner rather than later.
Read Charlie Hore's article Mao out of context in International Socialism Journal issue 110 at www.isj.org.uk/index.php4?id=185&issue=110