( CNN ) -- As U.S. President George W. Bush wrapped up his tour of the Middle East , some of the region 's biggest investors were doing business in the U.S. U.S. President George W. Bush during a lighter moment on his Middle Eastern tour with Saudi Prince Salman bin Abdul Aziz . Saudi Prince Alwaleed bin Talal topped up his holding in U.S. banking giant Citigroup , as part of a $ 12.5 billion cash injection from a group of backers , including the Kuwait Investment Authority . The same day , the Kuwait Investment Authority also participated in a $ 6.6 billion boost for U.S. investment bank Merrill Lynch . They 're the latest in a long line of substantial investments emanating from the Middle East ; most made by Sovereign Wealth Funds spending the proceeds of the oil boom . What are they ? Sovereign Wealth Funds ( SWFs ) are not a new phenomenon -- the first was founded in 1953 -- but recently , they 've become much more active . In the past six months , in the financial sector alone , they 've taken stakes in Morgan Stanley , UBS and Bear Stearns , as well as Citigroup and Merrill Lynch . How much are they worth ? Figures vary as many of the larger funds do n't divulge valuations . Morgan Stanley says , combined , they could be worth as much as $ 2.5 trillion . Standard Chartered says the total assets managed in SWFs correspond to around 12 percent of the market capitalization of the NYSE , or about 42 percent of total stocks on the Tokyo Stock Exchange . Who owns them ? Sovereign Wealth Funds are n't solely the preserve of Middle Eastern royalty . Norway 's Government Pension Fund is one of the biggest SWFs in the world , worth an estimated $ 322 billion . Singapore , China and Russia also have sizeable funds . In fact , they 're all featured Standard Chartered 's `` Super Seven '' ; funds with more than $ 100 billion in assets . In recent years , more countries have jumped aboard the SWF wagon . Among the most recent are Chile 's Economic and Social Stabilization Fund ( 2006 ) and Venezuela 's National Development Fund ( 2005 ) . Where does the money come from ? The biggest single source of funding for the largest SWFs is oil and other commodities . As oil prices swelled , so too did government coffers . Excess foreign reserves are also a source of funding . And of course , as the value of their assets grows , SWFs too will have more money at their disposal . In ten year 's time , Standard Chartered estimates they 'll be worth $ 13.4 trillion . Morgan Stanley forecasts a more optimistic $ 17.5 trillion . Who are the big spenders ? The Abu Dhabi Investment Authority is the world 's biggest SWF , in dollar value , as well as a proportion of the Emirate 's GDP . Estimates of its size vary widely , from $ 250 billion to $ 1 trillion . Standard Chartered puts it about half-way at $ 625 billion . One of its most recent purchases was a $ 7.5 billion stake in Citigroup last November . Sounds great , what 's the catch ? Many commentators view the rise of SWFs as a positive force in the world market . For example , while the prospect of a recession in the U.S. has sent other investors running for cover , they 've been willing and able to pump vast sums of money into the U.S. banking sector . However , there 's some trepidation about their lack of transparency ; many do n't provide details of their size , investment returns or asset allocation . The secrecy has stoked concerns about their investment motives . Some countries are worried that SWFs will give other governments undue influence over important local companies . The challenge is to ease concerns about `` strategic investments , '' while not setting up too many barriers to foreign money . E-mail to a friend .
Strategic Worldwide Funds ( SWFs ) active buying power in major U.S. banks . First SWF founded in 1953 , now total worth worldwide stands at $ 2.2 trillion . Abu Dhabi has biggest SWF , followed by Singapore , Norway and Kuwait . List of some companies stoking controversy about strategic goverment stakes .