It maybe tells us something about priorities that the census lets us count the unqualified for only four censuses but graduates for six. However, definitions vary a good deal over time: For 1951, our figures are for people who remained in education past age 20. For 1971, the figures are for people with degrees or Higher National Certificates. For 1981, the definition is particularly broad, covering all with "degrees, professional or vocational qualifications", while in 1991 it is simply degrees. Unsurprisingly. the overall rate for England and Wales dropped from 9.7% to 7.2% between these two years. The 2011 data cover all with degrees, "NVQ levels 4 and 5; HNC; HND;", or formal medical or teaching qualifications.

Despite these complications, the geographical pattern changes very little over time, districts with high proportions of graduates being strongly concentrated into the south east.