selection bias corrected by Mills ratio (inverse of Gompertz mortality rate?)

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3659766  

`selection bias' using the inverse Mills ratio neglected by epidemiologists.

https://en.wikipedia.org/wiki/Mills_ratio

Mills ratio is the Survival function / pdf, 

The Gompertz function is u = - dS/dt * 1/S, so, HQ thinks Mills ratio is the inversion of the Gompertz mortality rate. 

related to 

https://en.wikipedia.org/wiki/Heckman_correction