Core Research Ideas
Fertility, Parenting, and the Future of
In survey research, many women express a desire for two or more children, while citing economic and social constraints that lead them to expect to in fact have fewer. Does this gap represent an opportunity for innovations or policies to improve wellbeing by investing in children and parents? What will be the consequences for the economic and social welfare of future generations if low fertility becomes enduring negative population growth?
Future Wellbeing and Time Discounting in Economic Evaluation
Compelling arguments in the social welfare and ethics literature establish that the wellbeing of future generations matters just as much as the welfare of people alive today. But economists’ widely-used tools for the evaluation of programs and policies “discount” the importance of consequences for future people. What theoretical and practical tools could facilitate proper evaluation of consequences for present and future times, alike?
Social Welfare Functions and Population Ethics for Policy Evaluation
Important theoretical tools exist to evaluate social welfare in a way that aggregates the wellbeing of everyone equally. But tools developed at the research frontier are not widely used in public economics and social policy. Moreover, important theoretical questions remain. How can population social welfare functions that value the interests of everyone become more widely-used tools in policy evaluation?
Heritable Fertility is Not Sufficient for Long-Term Population Growth. 2021. Samuel Arenberg, Kevin Kuruc, Nathan Franz, Sangita Vyas, Nicholas Lawson, Melissa LoPalo, Mark Budolfson, Michael Geruso, and Dean Spears.
All leading long-term global population projections agree on continuing fertility decline, resulting in a rate of population size growth that will continue to decline towards zero and would eventually turn negative. However, a literature inspired by mathematical biology has suggested that because fertility is heritable (i.e., higher-fertility parents tend to have higher-fertility children) and heterogeneous within a population, long-term population growth must eventually be positive. In this research note, we show that heritable fertility is not sufficient for positive long-term population growth, for empirical and theoretical reasons. First, empirically, even higher-fertility sub-populations show declining fertility rates which may eventually be below replacement (and in some populations already are). Second, in a simple Markov model, because heritability is imperfect, the combination of heritability and fertility rates may be quantitatively insufficient: it may be that higher-fertility parents nevertheless produce too few children who retain higher-fertility preferences. These results underscore the importance both of understanding the possible consequences of long-term fertility decline and depopulation and of the causal importance of culture and choice in human populations.
Foundations of Utilitarianism Under Risk and Variable Population. 2021. Dean Spears and Stéphane Zuber
Utilitarianism is the most prominent family of social welfare functions. We present three new axiomatic characterizations of utilitarian (that is, additively separable) social welfare functions in a setting where there is risk over both population size and the welfares of individuals. First, we show that, given uncontroversial basic axioms, Blackorby et al.’s (1998) Expected Critical-Level Generalized Utilitarianism (ECLGU) is equivalent to a new axiom holding that it is better to allocate higher utility-conditional-on-existence to possible people who have a higher probability of existence. The other two novel characterizations extend classic axiomatizations of utilitarianism from settings with either social risk or variable-population, considered alone. By considering both social risk and variable population together, we clarify the fundamental normative considerations underlying utilitarian policy evaluation.
Temperature, Humidity, and Human Fertility: Evidence from 58 Developing Countries. 2021. Michael Geruso, Melissa LoPalo, and Dean Spears.
A critical open question at the intersection of climate change and demography is the relationship between extreme climatic conditions and human fertility. In this paper, we study how temperature and humidity exposure affects human fertility in the developing world. We combine 142 rounds of Demographic and Health Survey datasets from low and middle income countries around the globe to create the most complete catalogue of fertility patterns linked to weather data to date. Importantly, our analysis separates the direct impacts of weather from other place-specific seasonal factors that may influence fertility. We find that exposure to extreme heat—relative to a village or urban area’s typical seasonal temperature profile—lowers birth rates nine months later. We find that the rebound in fertility in subsequent months is incomplete, suggesting the fertility declines due to extreme weather are not completely reversed with later additional childbearing. These results have significant implications for climate change, both in describing the potential fertility consequences of climate change and because optimal climate policy depends crucially on the expected size of future generations.
Utilitarian benchmarks for emissions and pledges promote equity, climate and development. 2021. Mark B. Budolfson, David Anthoff, Francis Dennig, Frank Errickson, Kevin Kuruc, Dean Spears, and Navroz K. Dubash.
Tools are needed to benchmark carbon emissions and pledges against criteria of equity and fairness. However, standard economic approaches, which use a transparent optimization framework, ignore equity. Models that do include equity benchmarks exist, but often use opaque methodologies. Here we propose a utilitarian benchmark computed in a transparent optimization framework, which, could usefully inform the equity benchmark debate. Implementing the utilitarian benchmark, which we see as ethically minimal and conceptually parsimonious, in two leading climate-economy models allows calculation of the optimal allocation of future emissions. We compare this optimum with historical emissions and initial Nationally Determined Contributions. Compared with cost-minimization, utilitarian optimization features better outcomes for human development, equity, and the climate. Peak temperature is lower under utilitarianism because it reduces the human development cost of global mitigation. Utilitarianism, therefore, is a promising inclusion to a set of benchmarks for future explorations of climate equity.
Population Ethics and the Prospects for Fertility Policy as Climate Mitigation Policy. 2021. Mark B. Budolfson and Dean Spears.
What are the prospects for using population policy as tool to reduce carbon emissions? In this paper, we review evidence from population science, in order to inform debates in population ethics that, so far, have largely taken place within the academic philosophy literature. In particular, we ask whether fertility policy is likely to have a large effect on carbon emissions, and therefore on temperature change. Our answer is no. Prospects for a policy of fertility-reduction-as-climatemitigation are limited by population momentum, a demographic factor that limits possible variation in the size of the population, even if fertility rates change very quickly. In particular, a hypothetical policy that instantaneously changed fertility and mortality rates to replacement levels would nevertheless result in a population of over 9 billion people in 2060. We use a leading climate-economy model to project the consequence of such a hypothetical policy for climate change. As a standalone mitigation policy, such a hypothetical change in the size of the future population – much too large to be implementable by any foreseeable government program – would reduce peak temperature change only to 6.4°C, relative to 7.1°C under the most likely population path. Therefore, fertility reduction is unlikely to be an adequate core approach to climate mitigation.
We are now hiring for fall 2022. We are hiring for three roles to join our team. We are recruiting researchers across disciplines with expertise in economics, demography, and social evaluation. We will strive to recruit a diverse and inclusive team and plan to offer competitive salaries and benefits to attract outstanding scholars.
Research Scientists will collaborate actively with our team in the production of independent and coauthored research. Annually renewable while the research is successful and funded, potentially for years to come.
Self-directed Postdoctoral Researcher
Postdocs will conduct 100% self-directed research without teaching obligations, while also participating in program activities. Successful candidates will pair a 1-2 year postdoc with deferring the start of a new assistant professor position.
Predoctoral Fellow and Research Assistant
Predoctoral Fellows will support the research and activities of the program and participate in program activities, during a typically two-year period of preparation for a PhD.