Which of the following is NOT considered a disadvantage of index annuities?

Minimum guarantees are features commonly associated with index annuities that provide a safety net for investors. These guarantees ensure that even in unfavorable market conditions, the policyholder will receive a certain minimum return on their investment. This characteristic serves to protect the investor's principal, making it an attractive element rather than a disadvantage.

In contrast, lack of transparency, restrictive surrender charge periods, and interest credit timing are considered disadvantages. Lack of transparency can lead to confusion regarding how returns are calculated and what fees may be involved. Restrictive surrender charge periods can limit how easily a policyholder can access their funds without facing penalties. Interest credit timing refers to the specific periods during which interest is credited to the account, which may not align favorably for the investor during market fluctuations. Thus, these aspects can be seen as drawbacks compared to the protective nature of minimum guarantees.