How far should we blame the Chinese for the credit crunch? Traditional savers, they saved even more as they got richer and richer, and a fair chunk of it went into US government bonds. That kept US interest rates low, making Americans better able to afford mortgages. More loans were taken out, and property (along with much else) boomed.

But low-interest mortgages are bad news for banks. They want to charge more to borrowers than they pay out to lenders. That's how they make money. But at low interest rates there is not much room for that difference to work. So banks went for volume, expanding their mortgages and raising the cash in slices from investors and other banks.

Low yields looked OK when the market was expanding, but many investors seemed not to understand the risk of this high-flying strategy. They weren't helped in that by the rating agencies, who earn their fees from banks and are therefore reluctant to criticize them.

But eventually the kite began to come down, with US failures among the riskiest mortgage lenders, and the UK collapse of Northern Rock, whose business rested on their ability to carry on raising the funds they needed to keep the business growing.

The US and UK cut interest rates in the hope of helping customers to pay their loans and bankers to ride out their failures. But then the growing realism among bankers has caused them to raise the interbank rates on which this whole kite flew – shaving the lender-borrower margin still more. Ouch.

At least with quarterly reporting, most of the problem is now out in the open. It's uncertainty that really spooks markets, and perhaps now that analysts and investors can see the numbers, however bad they are, there's less of that uncertainty about. But every bit of bad news continues to give investors the jitters.

So the Chinese were at the root of it all. Or was it perhaps our own stupidity, and a regulatory system that props up failing enterprises (like Northern Rock) and makes businesspeople able to take absurd risks in the knowledge that taxpayers will bail them out?