Co-Op partner leveling faster than I do in Borderlands 2

I am playing Borderlands 2 in Co-Op with my husband. We have been playing everything together and don't play these charters without the other, but he is leveling faster than me. It started just as a little more than me and now at level 63 he is almost a whole level ahead. Anyone know why? He doesn't have anything equipped that would give him more experience.

Aside from experience boosting equipment there are three factors that can lead to diverging experience.

• +100xp for reviving an ally is personal. Do you go down often?
• You may be falling behind when your partner kills enemies. There is a certain maximum distance from the kill (or killing player) that experience gets awarded. I use to lead my wife's character along when she goes AFK to the baby.
• The player dealing the killing blow gets a slightly greater amount of experience. If your husband deals more damage, he'll get this bonus more often.

Other than that, experience is shared equally (copied, actually).

More info in this question: How does experience work in co-op?

+1 for family gaming!