Polymer compositions are described that are well suited for producing reflectors for light-emitting devices, such as light-emitting diodes. In one particular embodiment, the polymer composition contains a polymer resin, a white pigment, a silicone compound, and a nucleating agent. The polymer resin may comprise, for instance, a poly(1,4-cyclohexanedimethanol terephthalate). In accordance with the present disclosure, the composition also contains at least one silicone compound and at least one nucleating agent. The silicone compound and nucleating agent have been found to improve the molding processability and reflectance stability of the polymer composition.