The Romer Model turns 25: 25 years ago this month Paul Romer‘s paper, “Endogenous Technological Change” was published in the Journal of Political Economy. After over 20,000 citations, it is one of the most influential economics papers of that period. The short version of what that paper did was to provide a fully specified model whereby technological change (i.e., the growth of productivity) was driven not be outside (or exogenous) forces but, instead, by the allocation of resources to knowledge creation and with a complete description of the incentives involved that provided for that allocation. Other papers had attempted this in the past — as outlined in David Warsh’s great book of 2006 — and others provided alternatives at the same time (including Aghion, Howitt, Grossman, Helpman, Acemoglu and Weitzman) but Romer’s model became the primary engine that fueled a decade-long re-examination of long-term growth in economics; a re-examination that I was involved in back in my student days.
Recently, Romer himself has taken on others who, more recently, have continued to provide models of endogenous economic growth (most notably Robert Lucas) for not building on the work of himself and others that grounded the new growth theory in imperfect competition but instead trying to formulate models based on perfect competition instead. I don’t want to revisit that issue here but do want to note that “The Romer Model” is decidedly non-mathy. As a work of theoretical scholarship, every equation and assumption is carefully justified. The paper is laid out with as much text as there is mathematics. And in the end, you know how the model works, why it works and what drives its conclusions. ...
After explaining the contributions in detail, he also covers:
So why has work in this area somewhat petered out? ...
And ends with:
In summary, the Romer model was a milestone and led to much progress. It is a stunningly beautiful work of economic theory. But there is more to be done and my hope is we will see that happen in the future as the cumulative process that drives new knowledge can drive new economic knowledge as well.