AbstractDespite the growing demand for long‐term care (LTC), the uptake of private LTC insurance (LTCI) is low and even declining in the United States. One reason is the complexity of LTCI decisions. Researchers have therefore suggested to support decision‐making abilities. This paper shows, however, that such support would not unambiguously enhance functioning of the LTCI market. We analyze whether selection arises from two correlated but different decision‐making abilities at old age, education and numeracy, and interactions thereof with private information. Using historical data from the Health and Retirement Survey we find that education generates adverse selection, which is only partially offset by advantageous selection due to numeracy. In addition, individuals with greater decision‐making abilities make better LTCI choices, amplifying selection by education and numeracy. This points at a trade‐off between decision simplicity and selection in insurance markets and suggests other steps are needed to enhance the performance of private LTCI markets.