Driger is right that McEnroe is not responsible for the tennis boom. That peaked in 1974-5, fueled largely by the great Laver-Rosewall WCT matches of winter 1971 and spring 1972. Jimmy Connors's arrival in 1973, along with Bjorn Borg, also helped. Country clubs were talking about paving over golf courses for tennis courts, there were long lines for public tennis courts, and tennis on TV was like NASCAR now, sometimes second only to football. This can all be checked at any University library with back newspaper files or a back set of Nielsen TV logs - World Tennis and Tennis magazine issues are also useful. Lots of it is not yet archived on the web. By 1977-8, articles were already appearing about what happened to the tennis boom. A lot of the problem was conlicting playing circuits and confusing TV schedules including pre-recorded matches You could see Marty Riessen vs. Cliff Drysdale simultaneously on three channels! McEnroe, if anything, was partially responsible for the decline in popularity with his disruptive whining. His 0.0 rating on his talk show points out that he just doesn't fly with anybody but a few passionate fans who love to hear his worn-out act over and over like a bedtime story.