In professional tennis, there is a dominance of a small group of players. For the men, the "Big 4" of Roger Federer, Rafael Nadal, Novak Djokovic, and Andy Murray dominated by winning most of the majors and remaining at the top of the world rankings. For the women, Steffi Graf, Martina Navratilova, and Serena Williams all spent over 300 weeks as the world number 1 in the rankings. Chris Evert and Martina Hingis both spent over 200 weeks at the top. Does this indicate an absence of competitive balance on the ATP and WTA tours?