Moreover the action risk-return relationship examined bu the CAPM, it is therefore not clear what factor other than the market risk ro Beta should give a return exactly equal to the risk-free rate. Black,Jensen, and Scholes exhaustively studied security returns on the New York Stock Exchange over a 35-year period and found instead that the measured zero Beta rate of return exceeded the risk-free rate. implying that some unsystematic (or non-Beta)risk makes the return higher for the zero-beta portfolio than is predicted by the CAPM. Moreover, the actual risk-return relationship examined by Black, Jensen, and Scholes appeared to be flatter than that predicted by the CAPM. It is therefore not clear what factors other than the market risk premium are being valued in the marketplace. According to the CAPM, it is only market risk that matters, since unsystematic risk can be diversified away. Much research is currently underway that attempts to examine whether factors other than Rm affect market risk.