There's a new drum beat running through the market jungle: ''double-dip, double-dip, will we have a double dip?"
The US Federal Reserve chairman will do what he can to soothe nerves today when he delivers his twice-yearly testimony to US legislators.
If you're only talking about the short term, the good news is that there's quite a lot Ben Bernanke can do to keep the US recovery on track. But for those that are worried about the long-term sustainability of the US and global recovery, there isn't much that he can say to help them relax.
People have been talking about the risk of a double-dip, almost since the recovery began - even though the pace of upturn, in most countries, has been on a par with recoveries in the past. That's because we are coming out of a major financial crisis, and the evidence of past such crises is that growth afterwards tends to disappoint.
Why are we worrying more about a double-dip now than we were a few weeks ago? One big reason is that the US economy appears to be growing more slowly than at the start of the year - and the growth in the first quarter has itself been revised down.
Retail sales in the US fell in June, for the second month in a row, and in the labour market, both average earnings and the number of hours worked have been going down. Most worrying, for monetarists - the money supply is still shrinking. That hasn't happened since the 1930s.
The other big fear is the eurozone: with so much talk of fiscal austerity, the worry is that if Americans stop spending, there even less scope for demand elsewhere to make up the gap.
That fear can be overdone - at least for this year. Greece, Ireland, Portugal have all announced bigger deficit cuts in the past few months - but they only account for less than a 1/6th of euro area GDP. Germany, France and the rest have really only fleshed out earlier fiscal plans - and their tightening doesn't really begin until 2011.
According to Credit Suisse, the extra tightening announced in the key euro countries in the past two months only amounts to about 0.2% of GDP over two years.
But we can safely predict that eurozone is not going to be a great engine of global growth. As I flagged at the time, the IMF now expects the euro area to grow by just 1.3% in 2011, compared to 2.1% for the UK and 2.9% for the US.
The UK has had its own version of the US debate in the past 24 hours, with the Treasury Select Committee highlighting that the budget has increased the probability of another downturn, and the news today that the MPC had discussed the possibility of extra measures to support the economy when it met in June.
I don't expect them to do anything any time soon - especially with inflation now likely to be above target for much of next year. But we can expect them to revise down their now far above-consensus forecasts for UK growth in next months' Inflation Report.
So, yes, it matters a great deal what happens to the US. In its last meeting the Fed's policy committee discussed the possibility of further measures to support the economy, for the first time in a while. Chairman Bernanke will surely entertain the possibility in his testimony later today.
If the bad news keeps coming, the US central bank has options. For example, it could go back into the market to buy mortgage-backed securities and/or US government debt; or it could say that it will not raise interest rates until inflation has reached a certain rate.
By all accounts, they would rather not do either: Kevin Warsh, an influential Fed governor, recently seemed to set a high bar for making fresh asset purchases. And when it comes to future rate changes, even the Fed doesn't want to tie limit its options too far in advance.
All that said, the record of the past few years tells us that the Fed will act if it has to. Those actions ought to be enough to prevent a double-dip.
But the Fed can't solve the basic problem, that the world is once again counting on US consumers - and spending in other deficit countries - to nurse it back to health.
Chinese exports are once again storming ahead. German exporters are doing well too, ably helped by the weaker euro. At the same time, the US - and British - trade deficits are once again going up.
None of this suggests a double dip is on the cards. But it does tell us that the global economy is struggling to learn new tricks.
Update 1817: As I mentioned earlier, many in the financial markets were looking for reassurance from the Federal Reserve Chairman in his latest report to US legislators. The US recovery has lost some momentum in recent weeks - investors wanted to know the US central bank will do everything it can to prevent a double dip recession.
In the event, Dr Bernanke acknowledged the fears hanging over the recovery in the world's largest economy but he did little to put them to rest.
He said the Federal Reserve was willing to take extra steps to support the economy - for example, by buying financial assets, or promising not to raise rates for a certain period of time. But he did not think they were called for yet - and he and his colleagues had not even decided which would work best.
US share prices fell on his remarks, but the dollar rose - and so did the price of US government debt. The yield on 10-year Treasury notes fell to 2.86, and the two-year yield hit a new low. However bad things get for the US economy, investors still seem to think it's safer there than anywhere else.