November 20th, 2009, 2:37 pm
this is back to stone age. you can input historical and no one will fault you. the point is, you can't hedge out your risk so you can only make assumptions, and you should make the most conservative one.eg, if it's a ccy that is pegged to USD, then use USD vol + conservative adjustment. if it's equity, then it can be historical + spread using a proxy stock with liquid option market + conservative adjustment