C4 is no longer open-ended. It's just that there's no standards body and no official list of calls. But lots of callers put out lists of the calls that *they* use at C4, and there's very broad agreement. Dancers have finally persuaded the callers that there are more interesting ways to make things hard than pulling out a call that no-one has heard for 3 years. Or the callers who called C4 in that style have all retired from calling C4, or something.

I think the number of people we invite to the Berkshires (an invitational C4 dance) is closer to 200 than 100. Add in the dancers in Japan that we don't know, and there are probably 200 that can dance C4 reasonably well.