There are two methods of dealing with the actuarial features of sickness insurance—the collective method and the reversionary method.

Unfortunately, perhaps the two methods have developed quite independently of each other, for historical reasons.

The collective method was used in Great Britain to investigate Friendly Society experience. The pattern for all subsequent investigations was set in the 1820s and brought to its culmination of refinement in Watson's Manchester Unity Experience still in the Institute's examination syllabus, 66 years after publication. No investigation of insured lives has yet been made in Great Britain. In the rest of this note the term ‘Manchester Unity method’ will be used to describe the collective method.