Avoiding Trade-Offs: Can population policies promote environmental protection and alleviate poverty?

Casey, Gregory, Galor, Oded | January 24, 2017 | Leave a Comment Download as PDF


Climate change has the potential to cause significant harm to people and the planet (Stern, 2007; Weitzman, 2007; Tol, 2011). Thus, a great deal of attention has been devoted to devising mitigation policies, such as carbon taxes, cap-and-trade schemes, and energy efficiency mandates. These policies have economic costs and environmental benefits. As a result, when economists try to calculate optimal climate change mitigation policy, they must weigh these costs and benefits (Nordhaus, 2013; Golosov et al., 2014). But what if there are policies for which there is no trade-off between economic and environmental priorities? Such policies could alleviate poverty and improve living standards while still providing much needed environmental protection.

We recently published a paper in Environmental Research Letters, “Is faster economic growth compatible with reductions in carbon emissions? The role of diminished population growth,” that demonstrates the potential for slower population growth to simultaneously increase income per capita and lower carbon emissions (Casey and Galor, 2017). Population growth is a major driver of carbon emissions, both historically and in projections of future emissions (Raupach et al., 2007). Yet, relatively little attention has been devoted to investigating the potential for population policies to influence global climate change (O’Neill et al., 2012). By population policies, we refer to policies that affect population growth via voluntary decisions made by individuals. Indeed, the entire reason to prefer policies that achieve both economic and environmental priorities is to improve the lives of individuals as they value them. 

Our Findings

Decreases in population also decrease overall economic activity, leading to less carbon emissions. At the same time, there are many mechanisms through which decreases in population growth – especially when driven by fertility – increase output per person. Thus, decreases in population growth have two offsetting effects on carbon emissions: the direct decrease in economic activity and the increase in economic activity per person.

Our paper measures the overall effect of decreases in population growth on carbon emissions in a two-step process. First, we use cross-country data to estimate the elasticity of carbon emissions with respect to population and income per capita. Consistent with existing literature, we find that the elasticity with respect to population is nearly seven times larger. Thus, decreases in population growth could decrease overall emissions while still substantially increasing income per capita. The remaining step is to estimate the impact of lower population growth on income per capita. To do so, we focus on the example of Nigeria and use a recently constructed economic-demographic model to estimate the effect of lower fertility on economic outcomes (Ashraf et al., 2013). We find that reductions in fertility can simultaneously lead to a 15% increase in income per capita and a 35% decrease in carbon emissions by 2100 C.E.

Thus, our analysis demonstrates the potential for decreases in population growth – via decreases in fertility – to simultaneously achieve economic and environmental policy priorities, circumventing a trade-off central to most climate change mitigation policies. Our analysis demonstrates the potential for these outcomes, without providing estimates of effects on a global scale or in response to specific policies. We hope that future work will extend our analysis in these directions.

Policy Implications

Our results have important implications for climate change policy. There are two reasons why population-based approaches may garner more political support than more conventional policy options. First, the principle of differentiated responsibility is widely accepted in the international community, and population policies have the potential to let high-fertility, low-income countries decrease emissions without imposing an undue burden on poverty alleviation and economic prosperity (Brunee and Strick, 2013). Moreover, by eliminating the trade-off between environmental and economic outcomes, population-based policies may be able to overcome free-rider effects that hamper efforts to address problems that are global or international in nature (Stavins, 2011).

Our research abstracts from the specifics of population-based policies and focuses instead on an exogenous reduction in fertility, but considering specific policies is obviously an important component to future work. There are several policies that may lead to lower fertility, the most obvious of which is the provision of contraceptives. Evidence suggests that there is a significant unmet demand for contraceptives in developing countries (Gillepsie et al., 2013). Moreover, a recent study for the Copenhagen Consensus Project suggests that policies targeting fertility via contraception have high returns (Kohler and Berman, 2014). Our earlier paper on the subject provides a broader discussion of the types of policies that could affect fertility in both developing and developed countries, focusing on the economic factors that alter individuals’ incentives (Galor and Casey, 2014). As with all decisions, parents have limited resources to allocate to raising children, and as a result, many economic policies will influence fertility rates. In particular, parents must decide how to allocate resources between having more children and investing in the future of each child. There is considerable evidence for this `quantity-quality trade-off’ in the economics literature (Guinnane, 2011; Galor, 2012). Thus, policies that increase incentives for investment in education, for example, can also lead to lower fertility levels. Such policies could include targeted interventions, such as subsidies for education, or broader macroeconomic interventions, such as increases in the potential for high-skill migration or subsidizing industries that demand skills from local workers (Galor and Mountford, 2008; Wheeler and Hammer, 2010; Docquier and Rapoport, 2012).


Most policies aimed at mitigating global climate change face a trade-off between economic and environmental outcomes. By contrast, our recent paper provides evidence that population-based policies may have the ability to simultaneously increase income per capita and lower carbon emissions. This suggests that these policies could play an important role in the global response to climate change.  They may also receive increased political support by lessening challenges of international burden sharing and free-rider concerns.


Ashraf, Quamrul H., David N. Weil, and Joshua Wilde. “The effect of fertility reduction on economic growth.” Population and Development Review 39, no. 1 (2013): 97-130.

Brunnée, Jutta, and Charlotte Streck. “The UNFCCC as a negotiation forum: towards common but more differentiated responsibilities.” Climate Policy 13, no. 5 (2013): 589-607.

Casey, Gregory, and Oded Galor. “Is faster economic growth compatible with reductions in carbon emissions? The role of diminished population growth.” Environmental Research Letters 12, no. 1 (2017): 014003.

Docquier, Frédéric, and Hillel Rapoport. “Globalization, brain drain, and development.” Journal of Economic Literature 50, no. 3 (2012): 681-730.

Galor, Oded, and Andrew Mountford. “Trading population for productivity: theory and evidence.” Review of Economic Studies 75, no. 4 (2008): 1143-1179.

Galor, Oded. “The demographic transition: causes and consequences.” Cliometrica 6, no. 1 (2012): 1-28.

Galor, Oded, and Gregory Casey. “Benefits and Costs of the Population and Demography Targets for the Post-2015 Development Agenda” (2014).

Gillespie, Duff, Saifuddin Ahmed, Amy Tsui, and Scott Radloff. “Unwanted fertility among the poor: an inequity?” Bulletin of the World Health Organization 85, no. 2 (2007): 100-107.

Golosov, Mikhail, John Hassler, Per Krusell, and Aleh Tsyvinski. “Optimal taxes on fossil fuel in general equilibrium.” Econometrica 82, no. 1 (2014): 41-88.

Guinnane, Timothy W. “The historical fertility transition: a guide for economists.” Journal of Economic Literature 49, no. 3 (2011): 589-614.

Kohler, Hans-Peter, and Jere R. Behrman. “Benefits and Costs of the Population and Demography Targets for the Post-2015 Development Agenda.” Copenhagen Consensus Center Population and Demography Assessment Paper (as of 3 October) (2014).

Nordhaus, William D. The climate casino: risk, uncertainty, and economics for a warming world. Yale University Press, 2013.

O’Neill, Brian C., Brant Liddle, Leiwen Jiang, Kirk R. Smith, Shonali Pachauri, Michael Dalton, and Regina Fuchs. “Demographic change and carbon dioxide emissions.” Lancet 380, no. 9837 (2012): 157-164.

Raupach, Michael R., Gregg Marland, Philippe Ciais, Corinne Le Quéré, Josep G. Canadell, Gernot Klepper, and Christopher B. Field. “Global and regional drivers of accelerating CO2 emissions.” Proceedings of the National Academy of Sciences 104, no. 24 (2007): 10288-10293.

Stavins, Robert N. “The problem of the commons: still unsettled after 100 years.”  American Economic Review 101, no. 1 (2011): 81-108.

Stern, N.H., 2007. The economics of climate change: the Stern review. Cambridge University press.

Tol, Richard SJ. “The economic effects of climate change.”  Journal of Economic Perspectives 23, no. 2 (2009): 29-51.

Weitzman, Martin L. “A review of the Stern Review on the economics of climate change.” Journal of Economic Literature 45, no. 3 (2007): 703-724.

Wheeler, David, and Dan Hammer. “The economics of population policy for carbon emissions reduction in developing countries.” Center for Global Development Working Paper 229 (2010).

The MAHB Blog is a venture of the Millennium Alliance for Humanity and the Biosphere. Questions should be directed to joan@mahbonline.org

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  • Time to take a good hard look at what is going on!

    Yet again the attention and blame is put upon those who have the least responsibility for present day climatic problems, have generally not contributed to wars, deforestation and the shameful abuse of all of Nature upon Earth. Once more GREED is cloaked in population issues. But for the extreme greed and abuses of a few, billions are starving and suffering and the blame is put upon them and their families. How about a fairer distribution of wealth to end extreme poverty issues? How about a fresh look at what so called development has led to for nature and the majority of people on Earth? How about an end to war and the making and selling of weapons of war for money to line the pockets of those who have too much already? This is what fuels mass migration problems. How about an understanding about intelligence and development based upon caring and sharing? How quickly we’d contribute to a cleaner healthier world, if development was not based upon a form of slavery where the majority do the hard back breaking work for meagre finances and a few get stupendously rich; at the potential cost of all species and future generations. How about some fresh insight into what’s really going on, instead of following the same old habits and thinking patterns, which endorse unbridled greed as a form of success instead of sickness and which cause a great deal of climate, fresh clean water, food and energy problems? These problems which will affect virtually everybody if not dealt with in a cohesive manner, could still be dealt with; if we wish to do so and stop destroying and wasting nature and life while creating more and more rubbish. The poor cannot even afford to create the technology to bring about so much harm.. How about rethinking about what defence means and defending life on Earth from human greed and stupidity while there is still possibly time. If we don’t all of our families and children will pay the price with their sweat and tears and we who can still make a difference, will all be responsible for their suffering.

  • Diogenes60025

    The pharisees of the Administrative State seek to compel all the Others to cease reproducing, while they continue to do as they please.

  • Didem Aydurmus

    Hi, I welcome any study that looks at population growth. I am not sure if voluntarily democratic governments will go down that road. My dissertation has a chapter on the topic. And is available here:

  • Megan Kmon

    It’s great to see yet another MAHB piece on population reduction, but I don’t think it goes far enough.

    First, a sustainable world will inherently be a world with significantly smaller human populations than we have now, so advocating for a reduction in population growth is just tinkering at the fringes. While focusing on the countries with the highest fertility rates (i.e. those that have not yet undergone “demographic transition”) is good, it neglects the reality that most countries still need to shrink their populations, not just slow growth.

    Second, while smaller populations (or less growth) will indeed create more economic and other opportunities, framing arguments around economic growth misses the point that a transition to a sustainable world will involve economic de-growth followed by steady state dynamics. It’s crucial that we continually speak to, and frame policy recommendations, within this paradigm.

  • The richest 1 billion population with a TFR of 2 and household incomes of $12,000 or more emit 13 times as Much CO2 as the poorest 1 billion with incomes less than $900 and that have 4 or more children.

    • Didem Aydurmus

      So rich people should have less children! 😉