Dissatisfied by this state of affairs, he sought answers by probing the non-rivalrous nature of knowledge: the fact that ideas, once created, can be endlessly exploited. The firms or individuals that come up with new ideas can only ever capture a small share of the benefits arising from them; before long, competitors copy the original brainwave and whittle away innovators’ profits. In Mr Romer’s work, markets are capable of generating new ideas. But the pace at which they are generated, and the way in which they are translated into growth, depends on other factors—such as state support for research and development, or the protection of intellectual property.
The “endogenous” growth models produced by Mr Romer, and by others influenced by him, were once hailed as a critical step towards understanding patterns of economic growth across the globe. They have not quite fulfilled that promise: knowledge may be necessary for growth, but it is clearly not sufficient. But their shortcomings have themselves raised important questions about the stubborn disparities in growth rates. Why are some countries able to exploit existing ideas and grow, while others are not? Should policymakers who want to boost growth focus on policies that support the creation of knowledge or on those that break down barriers to the exploitation of existing knowledge? Or does it make most sense to shift people and resources from the parts of the world that struggle to grow to those that do not? By provoking such questions, Mr Romer’s work identified a rich vein for other researchers to mine.
Mr Nordhaus, for his part, has been a towering figure in the debate about how to respond to one of the biggest challenges that humanity faces. When he was beginning his career in the early 1970s, awareness of the dangers of environmental damage and the threat posed by climate change was just starting to grow. Understanding the economic costs such damage imposes is essential to answering the question of how much society should be willing to pay to avert it.
Mr Nordhaus applied himself to solving this problem. That meant working out the complex interactions between carbon emissions, global temperature and economic growth. He combined mathematical descriptions of both climate and economic activity into “integrated assessment models”. This allowed him to project how different trajectories for the world’s carbon emissions would produce different global temperatures. That, in turn, allowed him to estimate the likely costs of these different scenarios—and thus what level of reduction in emissions would be economically optimal. He was the first to suggest that warming should be limited to no more than 2°C higher than the world’s pre-industrial temperature. Models like his have become the linchpin of most analysis of the cost of climate change.
