Larks comments on More empirical data on ‘value drift’

[Larks]

For instance, if the drop out rate for the most engaged core is:

Year 0-5: 10%

Year 5-10: 7%

Year 10-30: 15%

Then, the chance of staying involved the rest of their career is about 70%, which would mean the expected length of engagement is very roughly 20 years.

Are you assuming quite short careers? Using bucket midpoints I calculate

(20-0.1*2.5-0.07*7.5-20*0.15)/​(1-0.1-0.07-0.15)

Which suggests you are using ~24 years for a full career, which seems a little low. If I substitute 40 years I get over 30 years of engagement.

0.1*2.5 + 0.07*7.5 + 0.15*20 + (1-0.1-0.07-0.15)*40

The answer does not change very much when I converted these numbers to annualised risk factors in excel (and assumed 100% dropoff at year 40).

[Benjamin_Todd]

I was doing a very hacky calculation—I’ll change to 30 years and mention your comment.