Pre-print, Working paper: The purpose of this paper is to examine the alternative explanatory factors of the so-called long term care insurance puzzle, namely the fact that so few people purchase a long term care insurance whereas this would seem to be a rational conduct given the high probability of dependence and the high costs of long term care. For that purpose, we survey various theoretical and empirical studies of the demand and supply of long term care insurance. We discuss the vicious circle in which the long term care insurance market is stuck: that market is thin because most people find the existing insurance products too expensive, and, at the same time, the products supplied by insurance companies are too expensive because of the thinness of the market. Moreover, we also show that, whereas some explanations of the puzzle involve a perfect rationality of agents on the LTC insurance market, others rely, on the contrary, on various behavioral imperfections.