Assume the following model is applying to an asset
APT
E(Ri)=Rf+b1(Rm-Rf)+b2a2+b3a3+...+bnan+e
Macroeconomic model
Ri=E(Ri)+b'1a'1+b'2a'2+...+b'na'n+e
"where E(Rp) is the expected return from APT equilibrium in the absence of any surprises (of course market premium is included as well, so using CAPM will result the same.)"
the absence of any surprise do not apply to the market risk premium.
In the APT model , the market risk premium = Rm- Rf
In the macro economic model, there is no market risk premium,only hava'1,a'2, which are the surpriese = actural factor figure- predicted factor figure ( which is not the Rf)
So if there is no surprise in any other factor, assum a'1,a'2..=zero
Macroecomoic model Ri=E(Ri)=Rf+b1(Rm-Rf)+b2a2+b3a3+...+bnan+e
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