Birth Rates and Population Growth: How Many People can the Planet Support?

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When we talk about the future of democracy, the future of social institutions, and the future of the environment, we recognize that there are some trend lines that run beneath all three and these trends will have a driving impact one each future individually and on all of them combined.

One of these may seem, at a glance, to be the simplest trend line of all: fertility and birthrates.

The bottom line on birthrates looks simple at a glance. Measuring the number of literal people in the world is easier than aggregating all the complex metrics that contribute to, say, the global economy. How fast is the population increasing? Is it too fast or not fast enough for sustainability?

But of course nothing is as simple as it seems. A rapidly falling birthrate in one country may generate worries about that country’s tax and labor base, but globally, this drop may be offset by a spike in another region that welcomes a burgeoning labor force but worries about resource availability.

Are there too many people? Are there not enough people? A yes or no answer simply won’t suffice.

The best way to get to the bottom of this puzzle is to gather all the data available—not one trend line, but dozens of them—and draw what conclusions we can by weighing each against the others. In the US, the population has trended precipitously upward in recent decades, but much of the increase has been due to immigration, not birth. In good news for the environment, US birthrates have slowly trended down, but not in all age demographics.  

And before we can cheer or worry over a specific data point, it’s a good idea to settle on a shared definition of “sustainable” rates. Those who would like to see a robust labor force see gloom in every dip, but those concerned about water resources in southwestern population centers might worry if birthrates inch too high before water and agricultural problems can be solved.

And of course, the subject of “correct” family size is both emotional and personal, even as personal decisions, cultural trends, and the reasons behind the trends shift from year to year. For example, some women may choose to have fewer children than they actually want due to economic pressures and concerns about college tuition and childcare costs. But within a year or decade, specific concerns give way to others, and the priorities and life-stage of a potential parent evolve and change over time. Throughout the fertile years of a person’s life, factors that drive birth decisions change as the landscape changes.

But as it happens, each person’s decision to have children will have a long-term impact on all of us. That impact is hidden somewhere in a vast field of population data.

Here are a few quick fertility-trend overviews provided by the Pew Research Center:

Here’s a review of total birth rates by country in 2018 from the World Population Review:

Here are a few policy suggestions to combat declining birth rates, provided by the NIH:

Here’s an HHS manuscript summarizing research on the links between population and the environment:

For more ways to engage with this topic and support our efforts to build a sustainable world, contact the team at Just Atonement.