Currently I am working with huge data frame which consists of a lot firms. For each firm in my sample I calculated asset volatility ( I am using Merton default probability model, so I have used 2 equation approach to calculate asset value and asset volatility). Then I have divided my sample into parts (let s call them portfolios) based on industry and size factor. Now I would like to calculate the asset volatility of each part ( portfolio) in order to use it in the analysis. My problem is that I cannot calculate pairwise correlation between firms in the same portfolio and that s reason I have directed myself here.
Possibly you have heard about the modeled volatility of KMV Merton model which you can access:
I want to approximate their calculations but as it is not elaborated there I would kindly ask you suggestions.