Debbie wrote: "Only a small subset of the population of any given surname emigrated to America." I have been wondering if that small subset is more like X% of the families emigrating or X% of each family emigrating. I lean towards the latter in the case of the Fergus(s)on because when you look at the distribution of our earliest known ancestors in the UK they pretty much blankets Scotland and Northern Ireland where our name originates; see http://dna.cfsna.net/UK.htm

We don't really know the answer to questions such as this because the research has not yet been done. You can be sure however that all those emigrants were not thinking of future generations and that they did not make a conscious effort to ensure that a representative from each known lineage emigrated to America. If you had 20 lineages in the British Isles in the 1600s you might well find that two or three of those lineages are represented in disproportionate numbers in America because people from the same area who were more likely to be related would have emigrated together. Brothers, cousins and neighbours would all travel together or follow each other out there. Some lineages will have died out and others will not have any descendants at all in America but might still have descendants in the British Isles or in Australia or New Zealand. Disproportionate numbers of people from Scotland and Ireland went to America because of the Highland Clearances and the Potato Famine, so it might well be that America is a better proxy for Scottish and Irish lineages than it is for English surnames. Have you tried doing a similar mapping exercise using the birthplaces given in the British censuses to see if there is a correlation? Debbie Kennett