I took a stab at the Einstein family. And it seems like there are 296 of them (44 non published listings) in the United States according to whitepages.com

I then searched in amazon.com and came up with this list:

albert einstein
alfred einstein
arthur einstein
bernice w einstein
blair einstein
bob einstein
bucky einstein
carl einstein
carol einstein
charles einstein
daniel einstein
david einstein
edwin f einstein
elisabeth roboz einstein
francine h einstein
gilles o einstein
h.a einstein
herbert h einstein
irving einstein
isidor einstein
jacob einstein
jeff einstein
joseph s einstein
leon einstein
lewis einstein
major b einstein
mara einstein
mark einstein
morris einstein
ned einstein
patricia einstein
paul einstein
pedro einstein
rosalie einstein
rosemary einstein
ruth einstein
siegfried einstein
stanley einstein
stephen j einstein
thomas h einstein
vivian einstein
vivian einstein gordon
walter otto einstein
xavier einstein

(I have excluded some hits that might be duplcates)

(a.h einstein)
(lewis d einstein)
(r. einstein)
(a.e einstein)

This sums up to 44 out of 296, which seems to be about 14.8%
or 44 out of 340 (including the 44 non published listings) which sums up to about 12.9%