Once you look at the numbers, you realize that beyond a certain size it doesn't matter much.
The standard deviation of health care costs for a company scales like 1/sqrt(# employees). Once (sigma cost) / sqrt(# of employees) << (mean cost), there is little advantage to having a bigger pool.
The standard deviation of health care costs for a company scales like 1/sqrt(# employees). Once (sigma cost) / sqrt(# of employees) << (mean cost), there is little advantage to having a bigger pool.