Down, down

The Nikkei fell around 11% during trading today, which means it is down more than 51% on its 12 month high. How long will it be before Mitsubishi UFJ's purchase of 21% of Morgan Stanley has to be called off as MUFJ decides to concentrate the money from its millions of Japanese investors in something less risky than a troubled American investment bank? A guaranteed 10% return on the putative investment is something not to be sneezed at but can MUFJ be 100% sure that their $9.2 billion is 100% safe?