Geek,
I ws under the impression your wife never intiated, but here you say she initiates 50% of the time. That ain't bad, some of us have a hard time getting our wives to initiate at all, in fact 50% sounds pretty fair to me. So I don't think the issue percentages, but more of one where she controls the amount of sex because she has the lower drive of the two of you. So maybe you need to be less of a sure thing, or perhaps be more assertive in a loving way when you are in the mood. Could be just as simple as you are losing on style points, KWIM? How about if you try different things, you know do a 180 in the bedroom. If you are the one in the mood, then it is incumbent upon you to do the intiating if you want to scratch that itch. Same goes for her. You two need to learn to talk to each other (sheesh, listen to me...like I listen to my own advice or something!).