October 20th, 2005, 3:09 pm
Given a correlation structure for the stocks in a basket and volatility surfaces for each of them, you should be able to compute the volatlity of options on the basket. There is obviously an upper bound to the basket's volatility (Jensen's inequality). Some will make the rough approximation of putting all correlation pairs equal to a constant. By doing so, you are able to extract from a basket's volatility and the volatility of its stocks, the implied correlation. If the implied correlation is above 1, they would sell the basket option and buy individual ones.