City sources predict the FTSE 100 will open down 20 points from yesterday's close of 5,744, extending Wednesday's losses of 32 points and tracking declines seen in Asia over night. Sentiment has been dampened by worries over the global economic outlook, with nerves building ahead of today's Jackson Hole summit as investors hope for further economic stimulus measures from the US Federal Reserve. Under-fire banking giant Barclays has promoted from within to fill its vacant Chief Executive Officer position, moving up Antony Jenkins, currently head of the Barclays Retail and Banking Business. Jenkins, who takes over with immediate effect, has been a member of the Group Executive Committee of Barclays since 2009 and has been with the company for nearly 30 years.Highly acquisitive advertising giant WPP is to move its headquarters back to the UK having moved to the Republic of Ireland in 2008 to escape Britain's taxes on overseas profits earned by multi-nationals. The decision was announced with the group's interim results which saw like-for-like revenue up 3.6% year-on-year and headline profit before tax rise by almost 12%, and more than 17% in constant currency terms, to £570m.Xstrata has said that the merger review process relating to its controversial tie-up with commodities giant Glencore is still ongoing in the European Union. "Xstrata understands that Glencore now anticipates that it will file formal notification of the merger with the European Commission in September," the mining firm said. The review process is still taking place in China and South Africa.