How about a ratio of home wins to road wins? The higher the ratio (presumably) the more active you are.

Its not perfect....... you can't say absolutely that a team with 40 home wins and 38 road wins is trying harder than a team with 38 home wins and 40 road wins. But a team that wins 30 at home and 50 on the road might raise suspicion.

I think any system is imperfect and I don't feel *GOOD* about any that are proposed including my own. But since we're brainstorming I thought I'd throw this out there and see if anyone can run with it.