75.347% to be more exact as determined by multiple supercomputers working in tandem. A press release for the world's media will be forthcoming.
Exp modifiers are additive: (base x bonus1) + (base x bonus2) + ... + (base x bonusX). There are other natural bonuses that mean turning on exp bonus in addition to these, you will not be calculating exp yesterday x bonus today difference.
About half and half? Of course I don't actually care about the 1% but something does seem to be off. On live at level 1 killing a white con gives exactly 10% exp (due to exp cap.) With the bonus exp they're giving 17.5%. So the only other explanation would be no matter what the exp event is you increase the exp cap by 75%?
If only we could write a program to gather up all those unused half percent xp bonuses floating around and deposit them into a private account...it's not like they belong to anyone, right?. Where's Richard Pryor when we need him?