  We present in this paper a compilation of the present status of experimental
delayed-neutron precursor data; i.e. beta-decay half-lives (T_1/2) and neutron
emission probabilities (P_n) in the fission-product region (27 <= Z <= 57).
These data are compared to two model predictions of substantially different
sophistication: (i) an update of the empirical Kratz-Herrmann formula (KHF),
and (ii) a unified macroscopic-microscopic model within the quasi-particle
random-phase approximation (QRPA). Both models are also used to calculate so
far unknown T_1/2 and P_n values up to Z=63. A number of possible refinements
in the microscopic calculations are suggested to further improve the
nuclear-physics foundation of these data for reactor and astrophysical
applications.
