Another week, another instalment of Sub-Prime! – the reality show in which viewers get to guess which bank is going to be the next to shock us with revelations about the scale of its financial insobriety back in those heady days of easy money and disappearing risk premiums.

Actually, yesterday’s big news didn’t really represent a new instalment in the long-running series, more like one of those what’s-happened-so-far clarifications that you sometimes get at the start of a new episode.

The travails of Citigroup, America’s largest bank, were already well known - $10 billion (£4.8 billion) in losses on asset-backed securities; one chief executive ousted – but yesterday it was hit again when Goldman Sachs upgraded its estimates for the bank’s total likely losses from the debacle to $15 billion and downgraded the company’s stock recommendation from “hold” to “sell”. Given the rarity of a “sell” recommendation on Wall Street, even in those days of greater enforced transparency, it means something like: “Run, do not walk, to your broker and get every last penny you can out of this dog of a company while you still can.”

I thought Goldman Sachs did a pretty good job of disguising the schadenfreude in their rather stony observations about their less fortunate banking brethren. Goldman, of course, has reason to strut a bit, since it seems that, unlike those oiks at other institutions, its managers managed to exit the gadarene rush into CDOs and the like just before the cliff’s edge.

But we can be certain there will be more instalments of the sub-prime saga – and who knows who may yet be exposed? As grim as it all seems, the really important question for investors in America and elsewhere remains: how does all this affect the great American consumer? We may get answers in the next few days.

Thursday is Thanksgiving Day, when the nation actually stops spending for a few hours and gives thanks for its many blessings.

In recompense for this unconscionable lapse and inexplicable misplacing of national priorities, the country goes completely crazy the next day and kicks off the Christmas shopping season in a frenzy of retail activity.

It is known in the trade as Black Friday. The name is not a reference to the colour of turkey stuffing after it has been left on the table too long; it reflects, instead, the fact that this is traditionally the biggest day for retail spending of the entire year as everyone gets off to an early start (by my standards) in their Christmas shopping duties. And so, for most retailers, it is the day that their annual accounts can be relied on to go into the black.

It is, thus, I believe, the only national holiday that I know of anywhere in the world whose popular name derives from the terminology of accountancy. (Please readers, spare me the e-mails telling me I have forgotten about Singapore’s Double-Entry Thursday, or Estonia’s Accruals-Basis Tuesday.)

This year the stakes on said Friday are higher than ever and retailers are leaving nothing to chance in an effort to maximise their sales. JC Penney, one of the largest department stores, has announced that many of its shops will open at 4am on Friday. If you’re afraid you might sleep in, the retailers will even arrange a wake-up call for you on your mobile phone so that you can get in line early enough to pick up that heavily discounted 86in high-definition TV.

All eyes will be on the numbers that the retailers report after this weekend. Any sign of the long-awaited retreat by consumers will be taken as sure evidence that the bottom is about to fall out of the US economy. Consumption expenditures after all, account for 70 per cent of US economic activity and, as I have noted before, there has not been a real consumer recession in America since the early 1990s.

Will this Christmas season be the time that record comes to an end?

The credit crunch seems to be having as yet only limited impact on spending. The vast majority of Americans, in fact, still have access to fairly easy money. The Federal Reserve’s reductions in interest rates have actually significantly lowered the cost of much consumer borrowing.

Incomes have been rising steadily, and, as grim as the equity market tumble may have been recently, anyone invested in the stock market (and, thanks to highly visible pension accounts in America, that means just about everybody) knows that their stock wealth has increased since last Christmas by 5 per cent or more.

Housing, of course, is different. If the value of your house falls, do you trim your spending because you feel less wealthy?

We are now in uncharted territory.

There has not been a sustained fall in American house prices since the early 1990s.

But even if we are in the midst of one now, will it really hurt spending? The latest figures from the Federal Reserve show that the total aggregate value of real estate held by the personal sector increased from $12.5 trillion in 2001 to $21 trillion in the middle of this year, a staggering 70 per cent increase in wealth in just six years.

My guess is that the price of your house would have to fall a fair bit before you decided to get seriously stingy with the Christmas presents.

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