thing is, that's such a hard thing to quantify.
...and yet, we see so many women who look to their husband for 'lines' in the ED, and he'll say she fell down the stairs, or whatever while the a-hole has obviously busted up knuckles or something. You see it on TV enough for it to seem like a cliche, but it really does happen, and guys will get away with it for years because the chick somehow believes she deserves it.
psychological abuse really happens but the victims, in the end, really believe they're deserving of the treatment they receive, meaning this law is probably going to be useless anyway.