Abstract
This paper investigates the weekly evolution of skills as measured by unique data from a widely-emulated early childhood home-visiting program in rural China. The design of the study avoids input endogeneity issues and lack of comparable measures of skills that plague previous studies. Skills, nominally classified as the same, in fact, do not appear to share a common unit scale across levels. They are produced by skill-lifecycle-stage-specific learning processes. A novel dynamic stochastic skill production model for multiple skills is developed, aligning with empirical evidence. The model explains the "fadeout" of measures of learning through forgetting or depreciation of skills.