Variation of a supercooled liquid's viscosity and relaxation time with temperature is currently related to the liquid's excess entropy over the crystal phase value, instead of its configurational entropy. This assumes that a liquid's nonconfigurational entropy is either equal to or proportional to the crystal's entropy. To examine its validity, we define an exact ratio R-TS, which is equal to 2 if the assumption is valid, and then determine R-TS from the available data on 10 liquids. Its value is close to 2 for o-terphenyl and glycerol and deviates from 2 for eight liquids. This shows that the nonconfigurational entropy of most liquids is not proportional to the crystal's entropy, which has consequences for the current use of the excess entropy in developing theories of vitrification and for computer-simulation of the entropy-diffusivity relations by using the inherent structure model.