Measure the complexity of one DTD versus another?

I was asked an interesting question on Friday.  Is there a way to
measure the complexity of our new DTD versus our old DTD?

I haven't come up with anything too concrete.  Our new DTD has far
fewer tags, but it's more rigid.  Based on that, I'd say the new is
less complex.  Unfortunately, I think the real issue is that because
it's more rigid, it's harder for off-shore companies to convert large
quantities of documents to the new DTD simply because it doesn't
accept as much "garbage" tagging.

Has anyone else answered such a question?  How did you do it?

Thanks,
Mattio