Julia and I file as "married filing jointly" which means from the government's perspective we're one financial unit that earned some money and donated some money. With my 30% (pre tax) and Julia's 100% (post tax), last year came to 40.5% overall (pre tax).

Talking about having separate numbers for the two of us does tend to confuse people, though, so we've switched to both of using giving 50% (pre tax).