It is easy to think, with tongue in cheek, of a variety of poll questions that are not really relevant to beards. (Are you left-handed? Has your appendix been taken out? Are you wearing dentures?) But here is a question that IS relevant:
At what age did you have to shave DAILY to avoid looking unshaven?
This is a question about growing speed a.k.a. growth rate, not about coverage or density, as those probably increased later.