Foreword

• In the eighteenth century, English cleric, economist and demographer Thomas Malthus claimed that population growth was bound to outrun the food available and he argued that there should be limits on reproduction. Since then, many others have continued to claim that there are too many people in the world and not enough resources to support growing populations. A recent twist on the usual terms of the population debate occurred in 1980 when economist Julian Simon challenged biologist Paul Ehrlich to the now famous Simon–Ehrlich wager. Ehrlich’s The Population Bomb, published in 1968, predicted famine and social upheaval if steps were not taken to reduce population growth (Webb 2020). After a long argument, Simon challenged Ehrlich to select five metals and a date in the future, betting that the price of the selected metals then would be lower than at the time of the wager, suggesting more availability rather than scarcity. Ehrlich selected five metals that he believed would be worth more in 1990 than in 1980, after adjusting for inflation. If, over ten years, prices rose, Simon would pay Ehrlich. If they fell, Ehrlich would pay Simon. In October 1990 Ehrlich mailed Simon a cheque, since the real price of the five‐metal basket of commodities had fallen by 36 per cent (Pooley and Tupy 2020) even though the global population had increased.


• In his Hayek Lecture, Steven Landsburg begins by telling us how people respond when asked: Does the world have too many people? Usually, the answer is a simple yes or no. He then asks: How do you know? To give an economist’s perspective, he presents a thought experiment based on considering costs (negative externalities) and benefits (positive externalities). He concedes that there is obviously a physical limit to population, but this is different to the question of whether the world is currently overpopulated, or will ever be.


• While Malthusians associate larger populations with negative externalities such as famine and assume there will be less of everything to share between humans, Professor Landsburg reminds us of the positive externalities that come with population growth. He cites Harvard economist Michael Kremer (1993), who suggests that the ratchet of human history over the last million years has been mostly upwards: ‘More people, more ideas. More ideas, more prosperity. More prosperity, more people.’ Landsburg argues that we have not reached the point where the world is overpopulated. In fact, he believes that the real problem may well be that the incentives to have children are not strong enough.


• In response, Dr Stephen Davies suggests that if we accept Landsburg’s premise that the world needs more and not fewer people, this raises two questions for economists. Firstly, does having fewer people constitute a market failure that requires correction by government action? Secondly, should economists view people who do not have children as imposing costs or at least not contributing to greater general benefit? Davies also points out that many  economic historians have argued that it was restrained population growth in western Europe that led to an economic revolution happening there, rather than in other parts of the world (Foreman-Peck 2009).


• As an economic historian, Davies then asks the following question. If population growth does indeed lead to innovation and economic development, why did sustained innovation and development not really start until very recently? The answer Landsburg tentatively gives is the
  one put by Julian Simon, that until the 1750s global population had not reached a level high enough to support sustained innovation (Simon 2001). The quantity of the ‘ultimate resource’ had not reached a critical mass.


• Davies also adds a warning that as societies become wealthier, they also become more akin to complex systems, which can be more brittle and prone to breakdown and failure. Even a small event can cascade to derail the entire system. Think of the release of Covid-19 from Wuhan, China, to the rest of the world. However, Landsburg would also ask us to think of a world where the people who developed the necessary vaccines had not been born.


• Davies contends that since the early eighteenth century the world has faced three previous crises of complexity and systemic stagnation, but in each case the innovative process has burst through. He argues that we are currently in such a situation, and asks whether innovation will triumph again.


• For Davies, the answer to Landsburg’s question ‘Is the world overpopulated?’ depends on whether you think this  fourth bottleneck of modernity will be overcome like the three previous ones. If not, the world is indeed overpopulated because the number of people has reached or gone well past a point of zero marginal return, i.e. the externalities of population growth and increased interaction will have become negative. If you are more optimistic and believe in the ingenuity of humankind to overcome such challenges, then Landsburg is right. Davies believes that we simply do not know whether the human species will succeed again.


• Davies tempers his pessimism by citing Deirdre McCloskey, who argues that the cycle of progress has continued thanks to liberalism and individualism (McCloskey 2019; McCloskey and Carden 2020), which has broken through
  social limits to growth and weakened any attempts by the ruling classes to stop innovation where they feel it threatens the status quo. Both Landsburg and Davies contend that we need to sustain economic, political, cultural and
  social liberalism – and individualism – for progress to continue and for us not to stagnate.


• Whatever your views, Landsburg’s economic analysis and Davies’s response as an economic historian help us to think about the many trade-offs to be considered in answering the question of whether the world is overpopulated or not.