Markets plunge as U.S. emergency stimulus and bank downgrades spook investors

As of this writing, Britain's FTSE 100 down 4.86%; France's CAC 40 down 4.90%;  German DAX down 4.39%; US markets yet to open. Japan's Nikkei 225 closed down 2.25%; Hong Kong's Hang Seng Index closed down 4.85%; Australia's ASX 200 closed down 2.63%.

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