Solow also was the first to develop a growth model with different vintages of capital.[2] The idea behind Solow's vintage capital growth model is that new capital is more valuable than old (vintage) capital because new capital is produced through known technology. Within the confines of Solow's model, this known technology is assumed to be constantly improving. Consequently, the products of this technology (the new capital) are expected to be more productive as well as more valuable.[2] Both Paul Romer and Robert Lucas, Jr. subsequently developed alternatives to Solow's neo-classical growth model.[2]
Since Solow's initial work in the 1950s, many more sophisticated models of economic growth have been proposed, leading to varying conclusions about the causes of economic growth. In the 1980s efforts have focused on the role of technological progress in the economy, leading to the development of endogenous growth theory (or new growth theory). Today, economists use Solow's sources-of-growth accounting to estimate the separate effects on economic growth of technological change, capital, and labor.[2]
Solow currently is an emeritus Institute Professor in the MIT economics department, and previously taught at Columbia University.