Tax.
Stock acquired by policyholders upon demutualization of a life-insurance company is taxable, as premiums paid were solely for the defined benefit, and not an accrual of value.
Dissent: Value was accrued beyond the level of anticipated benefit prior to the IPO.
https://d3bsvxk93brmko.cloudfront.net/datastore/opinions/2015/12/30/13-16548.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.