Quote: "but is that because there seems to be something fundamentally wrong with the baseline data as almost every sport has seen very big drops over the same period? I looked at the data last week (pure curiosity) and it seemed bizarre that lots of sports had seen big drops reasonably similar in % terms - if I saw data like that in my work, without being able to investigate, i'd suspect a data error.'"
Not sure about your source of data here is the data for the SE APS over the same period.
Swimming -7%, Football no change, Athletics +21%, Cycling +4%, Golf -9%,Badminton -5%, Tennis -17%, Equestrian -2%, Squash/Racketball -2%, Bowls -18%, Crciket -4%, Rugby Union -26%, Basketball -17%,Netball +18%, Boxing +12%, Table Tennis +52%, Mountaineering +29%, Snowsports -13%, Hockey -13%, Sailing -22%, Weightlifting -43%, Canoeing +15%, Gymnastics -20%, Volleyball -16%, Rowing -31%, Taekwondo +12, Rounders -7% Judo +11, Fencing -35%.
In terms of active participation over the same period rugby league has gone from 19th to 28th the biggest drop by any sport. This and the above figures clearly show, (discounting bowls) out of the top 10 sports only 1 had decrease of 10% or more. Only weightlifting suffered reduction anything like RL has reported.
Traditional summer sports sports that do not involve much expense seem to fair best but there is not a clear pattern. Since the figures vary so widely SE figures do not sound dubious but the previous figures of certain sports certainly look doubtful.