Analysts already have a name for the next six months of China's history. They are calling it “the great air pocket”. They believe that it will be a period of intense turbulence, a terrifying test for those in control, with an unknown fate on the other side.

Even before yesterday's worryingly bad CLSA PMI survey was released, there were clear signs that the severity of the economic turmoil faced by China has filtered through to the brains in Beijing. Private sector forecasters believe that GDP growth could fall below 6 per cent next year and conventional wisdom suggests that the pact between government and people is set up so that social stability starts to unwind if growth tumbles much below 8 per cent. Whether or not there is some flexibility to those numbers, the message is not lost on the Government, which has thrown an amazing $586 billion (£406 billion) at the problem, with pledges of more if necessary.

Its leaders have been at pains to tell crowds across the country that there will be more stimulus to come if the measures introduced now are not sufficient. Many analysts believe that China has the power to deliver protection from global turmoil through huge infrastructure projects providing jobs and growth. Even if export growth, manufacturing and retailing are still shockingly bad in 2010, say the analysts, these mega-projects should keep growth hovering at least above 7 per cent. The same analysts are predicting a precipitous drop in China's public finances as the projects begin to gobble the promised billions.

However, such measures will not take effect immediately and a critical six months lies ahead that will severely test both Beijing itself and those who cling to the belief that the Chinese Government still retains the power to micromanage what has becomea vast, market-driven economy. On one reading, Beijing's bluff has already been called and its powers found wanting. Wen Jiabao, the Prime Minister, has said that he has two worries: migrant workers returning home, and finding jobs for graduates.

He has good reason to be concerned because throughout the industrial heartlands the same scene is now playing daily: a bleak drama that seems a terribly long way from the dazzling economic spectacle once staged by China Inc.

The a morning shift arrives to find the factory gates firmly padlocked and a flimsy poster announcing the company's bankruptcy. The crowd's anger begins to froth as workers realise they are jobless, unpaid and that the owner has probably vanished back home to Hong Kong or Taipei. Depending on mood and numbers, the rage can easily get out of hand. In the days that follow, some hang around in the dwindling hope of finding work elsewhere; many simply pack up in despair and head back to the villages they abandoned five years ago in favour of the big cities.

The data suggests worse to come: officials believe that the world's largest light industrial zone, in the southern province of Guangdong, will see a fifth of its 45,000 factories close by March at the cost of some 3 million jobs. The Federation of Hong Kong Industries says that about 17,000 Hong Kong-owned factories could close across southern China, and provincial governments are predicting mass re-migrations of hundreds of thousands of people, very few of whom will find work. The problem for Beijing is how quickly and profoundly the returning migrant workers - and the dwindling job prospects for university graduates - undermine the whole show.

In the case of the migrants, their unhappy return home highlights the unevenness of Chinese economy growth and the postponement of the Government's much-heralded creation of a new middle class. But if the stimulus measures have not begun to work their magic by the summer, the spectre of large numbers of jobless, disappointed university graduates is, for Beijing, very alarming. The end of the six-month “air pocket” will coincide with the 20th anniversary of the crackdown on student protests in Tiananmen Square.

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