Yesterday's rout on global markets has spilled over into early trading today as losses continue across Asia.

Japan's Nikkei index closed down by more than 2% - while China's main market, the Shanghai Composite, has fallen by 1.2%.

The key S&P 500 market fell by 3.7% at one stage yesterday but pared back some of its losses to close 1.2% at 1860.

The 1830 level is seen as a key line in the sand and if the market falls significantly below this it could fall sharply by another 10 to 15%.

Key drivers....

• Concerns about China's unstable markets and slowing economic output.

• Oil and commodity prices have plummeted.

• US manufacturing is in recession and corporate earnings are falling.

• QE is possibly an exhausted tool which cannot make much difference anymore, outside of (possibly) Europe.

• The fallout from any debt defaults in emerging economies are likely to hit Western markets.

• Foreign banks have lent $3.6tn to companies in emerging markets in countries that are likely to struggle, particularly as rising US interest rates affect borrowings made in US dollars. Foreign investors hold an average of 25% of local debt in emerging economies.

Uncertainty in China and falling oil prices have unsettled traders, UK, French and Japanese markets have all fallen by more than 20% from their 2015 highs.

Investors withdrew some $52bn from equity and bond funds in emerging markets during the third quarter of 2015.

This has been attributed to the Fed's signaling that a rate hike was on the way, the fall of commodity prices, and increased global security threats - particularly in the Middle East.

As China slumps, Russia continues to lack economic firepower and growth in emerging markets stalls it is hard to see where stimulation for the global economy is going to come from.