Single child.
Now, nothing against 'Extropian, know thyself', far from it,
but we've been certainly poll-polluting the list way too
much lately. Kathryn stated correctly that self-answered
polls on electronic channels might be doubly biased. At
the very least we should move future polls to private
communications (whoever provoking a poll shall be charged with
gathering the result and posting the totals to the main list),
also, ExI might install some electronic (cgi-bin) poll
infrastructure, especially among the nonconnected extropians
(mundanes).
As to whether everybody on a listserv is an XNTX, a single counterexample should suffice. Removing self-selection-by-answering bias should be more difficult, but possible.
ciao,
'gene