Tennis was among the first major sports to offer equal pay for men and women in 1973; the result of Billie Jean King's lobbying formed the Women's Tennis Association and Wimbledon became the last of the four Grand Slams to pay equal prize money for men and women in 2007. There are several reasons why these recently expressed, somewhat neanderthal views are specious. Consider the claim that men work harder than women. In the specific context of tennis, the fact that men play five sets to women's three is considered the clincher. There are two linked counter-arguments here. One, the five-setters apply only to the four Grand Slams - and women have repeatedly said they would be happy to switch to the same format (so much for their "hormones and different stuff", as referenced by Djokovic). But in all other tournaments, men and women play three sets and some women's matches - including those in Grand Slams - last longer than men's matches.
Second, in the entertainment business, of which sports is undoubtedly a part, it is not longevity but skill and ability that determine spectator enjoyment, just as much as, say, movie goers don't pay more to watch a longer film. Andy Murray, world number two in men's tennis, at least, gets this; he sees no problem hiring a woman - Amelie Mauresmo - as his coach. The Moore/Djokovic argument that more spectators watch men's tennis than women is also hard to substantiate. Sure, Roger Federer and Rafael Nadal attract huge crowds because they are the most sensational players on the circuit. But so did the Williams sisters (the younger still does) or Steffi Graf or Martina Navratilova in their heyday. One indicator that spectators are not expressing gender preferences is that just as many women's matches are televised as men's, and top women tennis players are in the top ranks of endorsements and sponsorships.
Finally, there's the question of the negative loop. Gender pay parity in tennis has seen the rise of some of the most exciting talent in any sport: Martina Navratilova and the Williams sisters may never have been motivated to rise above their poverty and become the brightest stars of the sport without the incentive of making a decent living. It is likely that a whole host of women's sports could benefit from pay parity. Women's football, for instance, is still nowhere in the same class as the men's; but the steady rise in pay and prize money has seen it improve hugely over the past decade and a half. Today, pay parity is some distance away; according to a BBC study, out of 35 sports that offer prize money, as many as 25 offer the same amount to male and female champions, irrespective of the number of spectators or sponsorships. But it's not just in sports that this debate should be conducted with more seriousness. In Silicon Valley, where women still earn half to three-fourths of what men earn for the same qualification and work, that discussion is probably long overdue.