It came with a bang, on 12 June of this year. Since then prices have fallen 30 per cent on the Shanghai market, 40 per cent on the Shenzhen. About $4 trillion in paper values have been wiped out - but so what? Chinese stock prices are still far higher than they were a year ago. Indeed, at an average of 20 times earnings they are still overvalued by real-world standards.
Why would any government intervene over this? Some investors will win, some will lose, and it will all work itself out. But the Chinese government intervened in a big way. First it cut interest rates to the lowest level ever. When that didn't stop the slide in prices, it banned large investors (holding more than 5 per cent of a listed company's shares) and all foreign investors from selling their shares for six months.
It encouraged about 1300 Chinese companies - half the stock market - to suspend trading in their stocks. It forbade any new listings (IPOs) on the markets. It even ordered a state-backed finance company to make new loans to people who want to make bigger bets on the stock market than they can afford.
Anything and everything to stop the prices from falling, and lo! They did stop. Last week, prices even rose a bit.
This may just be what traders call a "dead cat bounce" - if the price falls from high enough, there is bound to be a little bit of a bounce at the bottom - but that is mainly of interest to Chinese investors. The interesting question for the rest of us is: why did the Chinese Communist regime do all this?
Because there are 90 million private investors in the Chinese stock markets. They tend to be older, they have been betting their savings on the market - and according to state media they have lost, on average, 420,000 yuan ($67,000) in the past six weeks.
That would be no problem if you were already in the market a year ago: you would still be well into the black. But a great many of the private investors piled in very late in the game - 12 million new accounts were opened as recently as last May - and they have already lost their shirts. They would have lost their skirts and trousers too if the government did not stop the collapse in prices.
So the regime intervened. This may be because the Chinese Communist Party loves the citizens so much that it cannot bear to see them lose. It is more likely to be because it is frightened that those tens of millions of stock-market losers (who were officially encouraged to invest) will start protesting in the streets.
This latest government action is part of a pattern that extends back to the global bank crisis of 2008, after which China was the only major country to avoid a recession. It did so by flooding the economy with cheap money. So few people lost their jobs, but the artificial investment boom created a bubble in the housing market that is now starting to deflate: millions of properties lie empty, and millions of mortgages are "under water".
Sooner or later, this game is going to run out of road.
The risk is that China's road ends where Japan's 30 years of high-speed growth ended in the late 1980s, with a collapse to 2 per cent growth or less and a quarter-century of economic stagnation. -Gwynne Dyer is an independent journalist whose articles are published in 45 countries.