US corporations have been relative winners out of the financial crisis so far, but a leading share analyst is warning that cannot continue.

"American companies winners?" you ask incredulously. "Didn't many go bust or have to be bailed out?"

Of course you're right, but the key term is relative winners.

While US unemployment remains stuck at 9.6 per cent (with the real unemployment and underemployment rates much higher), American corporate profits bounced back from the 2008 collapse.

According to figures compiled by Morgan Stanley's global strategist Gerard Minack in one of his notes to clients, US domestic profits increased by $US420 billion in 2009, while income to everyone else in the United States fell by $US377 billion.

He says this was part of the 'Great Swap', where the US government stepped in not only to take bad debts off the balance sheets of many US financial institutions, but also provided stimulus payments that propped up household income and consumer demand despite continued falls in employment and working hours.

Mr Minack says this benefited businesses because it allowed them to cut their domestic labour costs without having to wear the usual feedback response of their retrenched and underemployed workers cutting spending.

In this sense, stimulus worked exactly as Keynes' General Theory says it should - with the public sector (directly and through households) propping up demand for goods and services in place of flagging private demand.

But what Gerard Minack is arguing is that the US corporate sector has not been playing ball in this stimulus strategy.

Rather than keeping more workers on as the Treasury's money filtered through to its collective coffers, the US corporate sector continued cutting working hours right up to December last year.

After rising from lows below 4.5 per cent before the crisis to a peak of just over 10 per cent, the United States's official unemployment rate has only eased to 9.6 per cent - and it has been stuck in the mid-to-high 9 per cent range for the whole of this year.

This labour-related cost cutting has been among the largest factors pushing up corporate profits, but it is unsustainable, and Gerard Minack says it probably has already made the surge in US corporate profits unsustainable as well.

That is because the government has exhausted most of its handouts, and is not in a budgetary position to launch a new round of stimulus spending - especially in the face of renewed financial market pressure for austerity measures to reduce budget deficits.

Now it is up to the business sector in America to start playing ball and employing more staff.

Mr Minack says that will reduce their profit margins, as some of the costs they cut come back into the business, making profit growth much harder to achieve than it was immediately post-crisis.

However, an even worse scenario is one where businesses do not pull their weight by starting to re-employ.

While that will be good for the profit margins of each individual business in the short run, in the longer term it will mean households have less money to spend.

That will result in less money going into the tills of businesses, which means lower revenues that could outweigh the higher margins.

In turn, that might mean renewed layoffs, thus plunging the US in the downward spiral that government stimulus averted in the first place.

Except this time the government won't have much more fiscal ammunition to break the spiral into a double-dip recession, or to help reduce the severity and duration of this potential future downturn.

Gerard Minack puts this catch-22 for American corporate profits succinctly:

"If corporate America doesn't start to hire, profits will suffer in a double-dip. If they do hire - the base case - tepid recovery continues, but margin improvement will be much less substantial than last year," he wrote in his note.

"This, in my view, points to current earning forecasts being too high under almost any scenario. In a more-of-the-same growth scenario, too high; in a double-dip scenario, far too high."

If Gerard Minack is right (and he was one of the few with an inkling of the impending financial crisis before it broke) and US companies miss analyst expectations with their future earnings, there will be further share market volatility ahead.

Sitting here in the 'lucky country', it's easy to imagine the crisis has passed, or never existed at all, but there are a range of hazards ahead as the global economy still needs to undergo its biggest restructuring since World War II.

Michael Janda is the ABC's online business reporter