 that couples who do that will succeed. And I don't say that there's anything magic about sex, or maybe, but it's easily measured. I mean, if I ask you how many positive interactions did you have with your husband or wife in the last 48 hours, that's probably difficult for you to count. But if I say, well, how many times did you have sex and how many times did you fight, you can probably give a precise number. So for ease of counting, that's a useful index.