score:9
I have seen similar patterns in other parishes where I've been researching my own ancestors. A number of factors were at play, and it is difficult to be specific for a particular parish, however, the most likely reasons for Eversholt appear to be:
It's also worth observing that during the Commonwealth period (1649 - 1660) the parish registers were actually the personal property of a parish official (named, confusingly, the Parish Register). The records were often poorly kept, and many were simply removed by the Parish Register when his term in office ended.
When I was at school, the "received wisdom" was that people in the past didn't move far from where they were born. It seems we were misinformed. My personal experience is that my ancestors don't seem to have stayed in one place for more than a couple of generations!