Monday, August 27, 2018

Is a common approach to calibration reasonable?


"Model Calibration" article in Encyclopedia of Quantitative Finance states that



. . . a common approach for selecting a pricing measure Q is to choose, given a set of liquidly traded derivatives with (discounted) terminal payoffs (Hi)iI and market prices (Ci)iI, a pricing measure Q compatible with the observed market prices



where Q denotes



a probability measure on the set Ω of possible trajectories (St)t[0,T] of the underlying asset such that the asset price StNt discounted by the numeraire Nt is a martingale.




But we know that market prices (Ci)iI are generated by fallible human beings! Each of them has rather limited knowledge about "possible trajectories (St)t[0,T] of the underlying asset". Otherwise they wouldn't need the model we are trying to calibrate, would they?


So The Calibration Process receives some prices (Ci)iI, some arbitrarily choosen mathematical model (i.e. Heston) and produces as an output the calibrated model which supposedly able to give us predictions about the future (St)t[0,T]


Why do we believe that The Calibration Process is different from GIGO process?




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