Additive v/s Multiplicative (Discount/premium)

Hey Guys,

I just wanna know while measuring Discount or Control premium,etc sometimes we ADD them and sometimes we MULTIPLY… for instance , in build up approach we use to ADD all the premiums/risk factors like smaller size company, industry/company specific factors,etc. whereas, while measuring DLOM we multiply it with DLOC…plz throw some light on this !