of the actual quantity/ level of technology we simply refer back to our equation in levels. Knowing quantities of output , capital , labor and estimates for , and we can solve for as: Mankiw, Romer, and Weil augmented the Solow-Swan model with a human capital term. The explicit inclusion of this term in the model transfers the effect of changes in human capital from the Solow residual to capital accumulation. As a consequence, the Solow residual is smaller in the augmented Solow model: where: H(t) represents the human capital stock in an economy (the GDP) in some year, t. The associated regression to estimate this model is: Breton estimates the Solow residual for the human capital-augmented version of the Solow-Swan model over the 20th century. He finds that from 1910 to 2000 in 42 of the world's leading economies increased at an average rate of 1%/year and increased at 0.3%/year. Why the productivity growth is attached to labor The Solow residual measures total factor productivity, but the productivity variable is normally attached to the labor variable in the Solow-Swan model to make technological growth labor-augmenting. This type of productivity growth is required mathematically to keep the shares of national income accruing to the factors of production constant over time. These shares appear to have been stable historically in developing nations, and developed nations. However, Thomas Piketty's famous study of inequality in 2014, using a version of the Solow model, argued that a stable, relatively low profit share of national income was largely a twentieth century phenomenon. Critique of the measurement in rapidly developing economies Rapidly expanding countries (catching up after a crisis or trade liberalization) tend to have a rapid turn-over in technologies as they accumulate capital. It has been suggested that this will tend to make it harder to gain experience with the available technologies and that a zero Solow residual in these cases actually indicates rising labour productivity. In this theory, the fact that A (labour output productivity) is not falling as new skills become essential indicates that the labour force is capable of adapting, and is likely to have its productivity growth underestimated by the residual—This idea is linked to "learning-by-doing". See also Solow computer paradox is based on finding a zero residual in many countries even as information technology was becoming more widely available. Capital controversy over whether the level of capital in an economy