The intrinsic features of woker, ``ability' and ``motivation', are useful resources of human capital that makes profit for the firm. The purpose of the study is to examine how the firm designs the optimal wage policy when worker's intrinsic features are private information. The study follows the mechainsm-design approach, by which models with single, as well as double, intrinsic feature(s) of worker are established, and best ``incentive wage packages' are deduced. We finded out that, under single intrinsic feature, the firm's optimal wage package entails that, the more output the higher wages; under double intrinsic features, the firm must takes the relative strength of intrinsic features of the worker into account when making the optimal incentive wage package.

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