I'm going to preface my response with the following disclaimers:
1. My grandfather was adopted and I cannot find his biological parents, which wipes out one entire branch of my tree.
2. I have one documented incident of first cousins marrying (but I've heard rumors of more). This eliminates one set of 4th great grandparents.
3. In the last year I have been reworking my tree to ensure that every fact has a source, so my tree is still very small and I haven't made it past my 4th great grandparents, or into any other countries, yet.
So, with that being said, here is what I have:
However, if I remove the 252 ancestors from my grandfather's line and the 2 ancestors who are duplicates, my percentage is a little more favorable: a whopping 7%!
Either way you slice it, I have some work to do.
(I just didn't have the heart to calculate the percentage for 15 generations).
Do we share any ancestors?
Please email me at lostancestors [at] gmail [dot] com