No doubt new technology has been important, but there might have been another significant factor influencing generational changes: the number of aspiring pro pl

No doubt new technology has been important, but there might have been another significant factor influencing generational changes: the number of aspiring pro players. This number has increased dramatically in the last 30 years, but in the paper they only consider the number of successful players (roughly equivalent to the top X ATP rankings, where X is somewhere between 200 and 500). X has also been increasing, but at much lower rate, and as a result there are vastly more people competing for those X spots today than in 1980. It could be that to get into the top 100 today is as hard as it was to get into top 10 thirty years ago. As the natural selection gets more brutal, new players have to develop new, more effective skills to succeed.