In the 13th and 14th centuries, the richest people were overwhelming those whose names derived from places, whilst the poor tended to have names derived from crafts: Smith, Wright and suchlike. However, by the 16th century, this link between wealth and surnames had vanished; the rich were as likely to have craft surnames as the general population.
This, says Clark, suggests that there was complete social mobility, if we look at a long enough time-span.
You can probably guess that my pattern recognition bias and salience heuristic are going ape with this apparent correlation. What does this say about the entry to the early modern era?