BdB havde således bl.a. begrænset markedsporteføljen til de tyske aktier i CDAX, blot anslået parametrene ud fra, hvad der for en dels vedkommende var ældre data, uden at kontrollere, om de var gyldige for det pågældende investeringstidspunkt, afledt markedsrisikopræmien af en undersøgelse, der kun omhandlede den gennemsnitlige forrentning af tyske aktier i perioden 1954-1988, og — ved beregningen af betafaktorerne — betragtet CDAX-bankerne som virksomheder med samme forretnings- og risikoprofil.
Among other things, the BdB had restricted the market portfolio to the German shares making up the CDAX, had estimated the parameters solely on the basis of what were in part past data without checking their validity for the relevant date of the investment, had derived the market risk premium from a study that dealt solely with the average return on German shares in the period 1954-88 and, in calculating the beta factors, had regarded the CDAX banks as companies with the same business and risk profile.