Fears of a global slowdown triggered by US housing market woes wiped $5.2 trillion (£2.7 trillion) off global stock markets in January, say analysts.
Investors are wondering how long market problems will last
According to ratings firm Standard and Poor's, 50 out of 52 share indexes around the world ended the month lower.
Politicians also are concerned about the spiralling US financial problems.
On Sunday, finance ministers from the G7 group of industrialised nations said losses from the US mortgage crisis could reach $400bn.
The US Federal Reserve has previously estimated losses of up to $150bn after a surge in the number defaults on sub-prime loans.
Sub-prime loans are made to people with poor or non-existent credit histories.
Over the next two weeks banks are expected to report further write-offs of bad debt as the banking reporting season kicks off.
One of the major problems facing policymakers and analysts is that new losses linked to sub-prime problems keep emerging.
"The only thing we know is that it is big and we keep on discovering new dimensions," Italy's central bank governor Mario Draghi said after the G7 meeting.
"House prices keep falling (in the US) and subprime and mortgage sectors stay vulnerable."
JANUARY MARKET FALLERS
Turkey down 22.7%
China down 21.4%
Russia down 16.1%
India down 16%
Paris down 12.3%
London down 8.9%
New York down 6%
Source: Standard and Poor's
Uncertainty over the financial repercussions of the sub-prime crisis was reflected in stock market falls in January, according to Standard and Poor's figures.
Just under half of the major markets lost more than 10% of their value.
In London, the main FTSE 100 index lost almost 9% in January and 16.5% in the past three months.
In Paris, the stock market fell 12.3% in January and was down 15.3% in the three months from November. The falls wiped out all of the index's gains for the previous 12 months.
Emerging markets were hit even harder. China lost 21.4% in January, while Russia and India both fell 16%.