It's just the Fabrice Santoro effect
. He was hitting 30 years old around the start of that graph (1995) and as he get's older he just pulls the line higher and higher. Now that he's approaching 100 it's going to take at least 10 teenagers entering the top 100 to balance out his impact.
Groth, Tursunov, Nadal, Russell, Butorac, Nic Monroe, Marcus Willis