Players who are 30 years old+ may see their numbers move down the scale (towards 40), this is to create some balance with Junior players and to ensure full use of the 1-40 scale.
The guiding principle of the WTN is accuracy, whereby two players of a similar number should have a competitive match regardless of age. In reviewing the first two years performance of the WTN algorithm, the developers at the ITF have noticed an imbalance in players of a similar level where the age gap is higher. As such the ITF have made a correction to the algorithm to reinitialise players so that when they do play a player who is significantly older or younger of the same number, the result should be competitive.
At the same time it’s worth highlighting the accuracy of the number when in your own age group is exceptionally strong.