Who is favourite to be next Federal Reserve chairman?

Former US Treasury Secretary Larry Summers has withdrawn from the race to be the new head of the US central bank.

He had been seen as favoured by President Obama but was opposed by other Democrats and said any confirmation process would be "acrimonious".

Speaking to BBC World, George W Bush's former economics adviser Pippa Malmgren compared the merits of the other leading contenders to take over from Ben Bernanke.

"The market thinks Janet Yellen is the logical backup candidate... The White House is probably thinking more seriously about Tim Geithner."