Within the conventional neoclassical framework, a distinction is sometimes made between productaugmenting and factor-augmenting technical change. A parallel distinction is commonly made between and disembodied technical change with the former associated with factor, and the latter with product, augmentation. Disembodied change is commonly assumed to arise from increases in the stock of knowledge, independently of the characteristics of the inputs used, while change relates to increases in the efficiency of inputs, that is, labor skills or the productivity of physical capital. Unfortunately, this distinction is ambiguous. Changes in the efficiency of the inputs used are usually accompanied-indeed made possible-by increases in knowledge. And conversely, increases in the stock of knowledge often favor some inputs more than others, including the capital goods of one vintage relative to those of another. Notwithstanding the ambiguity, the concept of embodiment has intuitive appeal and this partly explains the focus on decomposing the sources of technical change that followed Solow's [6] seminal paper. But by the late 1960s, a reader of the literature might have concluded that such decomposition was impossible. For with merely time series data on inputs and output, product-augmenting and factor-augmenting technical change are empirically indistinguishable. In an important paper, Hall [3] showed that with data on used equipment prices and the interest rate, technical change and the deterioration function can, in principle, be calculated. However, the paucity of data on the price of used capital goods has allowed little progress in this direction. The new Longitudinal Research Database created by the U.S. Bureau of the Census now permits still another approach to the estimation of embodied technical change associated