Human capital has been proxied in several studies by years of schooling, educational attainment, and literacy rates. Years of schooling so widely used in human capital estimates that utilize both aggregate data and micro data. There are two reasons that come to mind immediately.
First, years of schooling is a useful indicator of capital accumulation. Particularly when there are no other readily available measures-either for individuals or with economy wide time series. Particularly, in cross-country comparisons, years of schooling is often the only feasible measure. Second, there is a theoretical argument that indicators that years of schooling is a measure of the stock of human capital under a reasonable set of assumptions. However, years of schooling is far from a perfect measure of the stock of human capital. First, estimates of the returns to schooling are sensitive to the correct specification of investment costs, but the overall conclusions concerning the importance of schooling are robust. Second, schooling produces only a part of the stock of capital. Some economists estimated that investment in on-the-job training produces 39 percent of the human capital.
Educational attainment can be a useful tool for comparing one feature of the human capital stock. However, they have several drawbacks: first, because completion of schooling does not certify a consistent set of skills; second, because it ignores less formal learning; third, because skills can depreciate, and fourth, because it can be hard to compare attainment by economic category.
Literacy rates give an indication of educational mobility between generations, which has a bearing both on equality of opportunity and the prospect of improving overall human capital stock. Literacy is a stock variable, but it involves important empirical problems; for instance, it does not account for the contribution of higher levels of education which tend to be crucial to productivity increases and, therefore, to aggregate economic growth.
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