This paper re-considers some of the evidence for low and declining social mobility in Britain, showing that one study based on a re-analysis of cohort figures appears to have had an impact on policy-makers out of all proportion to its scale and rigor. The study claimed to show that the income of parents and children were more closely related for sons born in 1970 than in 1958, and that therefore social mobility was declining. It also claimed to show that the incomes of fathers and sons were more closely related in Britain than in countries such as Norway. However, a reconsideration of the same results in this paper leads to very different conclusions. This example is considered in detail here to illustrate the point that it is not always a good thing for research to have influence. The most important and ethical challenge facing social research in education is to improve its quality rather than its impact. (Contains 1 table.)