In reduced density matrix functional theory, approximate total energy expressions in terms of the one-body reduced density matrix (1RDM) are minimized under the appropriate N-representability subsidiary conditions. The optimal 1RDM is in general nonidempotent. Measures of nonidempotency are the total charge of weakly occupied states and correlation entropy given in terms of the eigenvalues of the 1RDM. In this work, we calculate these quantities for several systems using different 1RDM functionals and compare with accurate results from a multideterminant method. Our goal is to assess 1RDM functionals with respect to the quality of the obtained 1RDM. © 2012 Wiley Periodicals, Inc.