to professor robert engle.looking at singles signals and hopefully they clarify but can a single american model workout with two or three or four america's? -- about that there could how about that bell curve? you got your first gray hair your sophomore year in college. all of the models are based on one curve -- usually a simple bell curve. but john edwards and others say thing -- forget about one curve when you have many in america -- the you buy it? -- do you buy it? >> we use many analyses. we allow the possibility of much more extreme events than would be predicted. that is the way the world is -- the world is continually a surprise so the bell curve does not capture that. fistfight going on among 300 people about who to blame for the financial crisis and steve roach and rabin he and all that -- robert engle stood up and quietly said -- we learned a lot. what did we learn? all thatrned first of the whole economy could be brought to its knees by a weak financial sector. >> its correlated together in the bel