The study looked at how people's choices in buying insurance policies can affect their mortality rates. By analyzing data from a U.K. insurance company, the researchers found that certain features of annuity policies, like payments to the estate and payment increases over time, were linked to different mortality rates. This suggests that some people may be choosing policies based on their health status, leading to a form of unfair selection in the insurance market. Interestingly, the size of the annuity didn't seem to affect mortality rates, which goes against what traditional insurance models predict. The pricing of different policy features also reflected these selection patterns, showing that people may be picking policies based on specific details rather than just overall size.