Registration 2017

[GeeTwo]

Sorting Mark's number by year yields:

Years Attrition
1 11.2
2 13.1
3 9.5
4 9.8
5 7.2
6 7.7
7 7.3
8 7.4
9 3.5
10 1.8
11 2.9
12 1.2
13 7.3
14 3.7
15 2.7
16 2.7
17 2.1
19 8.7
20 3.3
24 66.7

After smoothing through the values beyond 8 years, this looks a lot like the usual attrition rate - biggest after two years, second biggest after first year, then improving steadily from third year to a long-term team.