The United States sits squarely in Stage 4 of the demographic transition model, characterized by low birth rates and low death rates, with increasingly visible signs of drifting toward what some demographers call Stage 5. The country’s crude birth rate has been falling for over a decade, the death rate has actually risen in recent years, and the ratio between the two has narrowed sharply. Whether the US has already crossed into Stage 5 or is merely flirting with its edge depends partly on definitions and partly on how you weigh a few unusual features of American mortality that set it apart from peer nations.
A Quick Sketch of the Stages
The demographic transition model describes a broad pattern that countries tend to follow as they industrialize and modernize. In Stage 1, both birth rates and death rates are high, so population growth is slow and unpredictable. Stage 2 sees death rates plummet thanks to better sanitation, nutrition, and medicine while birth rates stay high, causing rapid population growth. In Stage 3, birth rates begin to fall as urbanization, education, and access to contraception spread. By Stage 4, both rates are low and roughly in balance, producing slow or near-zero population growth. Stage 5, still debated as a formal category, describes a situation where births fall below deaths and the population shrinks without immigration to offset the gap.
The US passed through Stages 1 and 2 during the 1800s and moved through Stage 3 across the late nineteenth and early twentieth centuries. Between 1835 and 1935, total fertility fell from around 7.0 children per woman to roughly 2.1, completing one of the most dramatic fertility declines in the industrialized world within a single century.1PubMed Central. Fertility decline in the United States, 1850-1930: New Evidence from Complete-Count Datasets The baby boom of the 1940s through early 1960s temporarily reversed the downward trend, but by the mid-1970s fertility had dropped back below replacement level and has generally stayed there, placing the country firmly in late Stage 4 for the past half century.
Where Birth and Death Rates Stand Now
The most telling numbers come from the last decade and a half. Between 2010 and 2023, the crude birth rate fell by about 18 percent. That decline was not steady: from 2010 through 2015 the rate dropped roughly 0.8 percent per year, then the slide accelerated to about 2.0 percent per year from 2015 through 2019 before leveling off into a period of fluctuation through 2023.2PubMed Central. Trends in Births and Deaths: United States, 2010-2023 Put differently, the US was already having fewer babies per capita, and then the pace of that decline roughly doubled in the second half of the decade.
Meanwhile, the crude death rate moved in the opposite direction, climbing about 15 percent over the same period. It rose an average of 1.0 percent per year from 2010 through 2019 and then fluctuated from 2019 through 2023, a stretch dominated by the COVID-19 pandemic’s toll.2PubMed Central. Trends in Births and Deaths: United States, 2010-2023 The combination of a falling birth rate and a rising death rate squeezed the birth-to-death ratio down by a total of 28 percent between 2010 and 2023. That ratio is the clearest single indicator of where a country sits in the demographic transition model, and the US trajectory points unmistakably toward the boundary between Stage 4 and Stage 5.
Why Birth Rates Keep Falling
If you are looking for one big explanation behind the post-2007 birth-rate decline, you will not find it, and that is itself a finding. The Great Recession clearly pushed births down in the early part of the slide, but once you account for that shock, researchers have been unable to pin the rest of the decline on any single economic, policy, or social change. The decline touched nearly every demographic group: teenagers, Hispanic women, and college-educated white women all saw birth rates fall.3American Economic Association (Journal of Economic Perspectives). The Puzzle of Falling US Birth Rates since the Great Recession Mechanically, the drop is linked to shifting birth patterns across successive cohorts of women passing through their childbearing years: women are starting families later, having fewer children, and in some cases not having children at all.
Several background forces play a role. Contraception is more effective and more widely used than a generation ago. The cost of raising children, especially housing and childcare, has climbed faster than incomes in many parts of the country. Women’s educational attainment has risen sharply, which historically correlates with lower fertility everywhere in the world. Cultural expectations around parenthood have shifted, too, with more adults reporting that having children is optional rather than expected. None of these individually explains the timing or pace of the decline, but taken together they create an environment where fewer people end up having as many children as earlier generations did.
America’s Unusual Mortality Picture
In the classic demographic transition model, Stage 4 countries enjoy long life expectancies and low death rates. The US partially fits that description, but its mortality story has an awkward wrinkle: compared with other wealthy nations, American adults die at unusually high rates, and the gap has been widening. At prime working ages of 25 to 64, Americans experienced death rates two to three times higher than their counterparts in other high-income countries as of 2018.4PubMed Central. Causes of America’s Lagging Life Expectancy: An International Comparative Perspective The age range of 25 to 44 has been hit hardest, and the disadvantage has deepened over the past decade rather than improving.
The drivers are strikingly specific. Drug overdoses, firearm deaths, and car accidents together account for a large share of the gap, particularly among men.4PubMed Central. Causes of America’s Lagging Life Expectancy: An International Comparative Perspective Beyond those external causes, the US is also falling behind on cardiovascular disease improvement, and deaths tied to metabolic, respiratory, and nervous system conditions have been climbing, partly reflecting higher rates of obesity.5International Journal of Epidemiology. US exceptionalism? International trends in midlife mortality The country now increasingly lags not just behind traditional peers like Japan, France, and Australia, but also behind Central and Eastern European countries that were far behind the US just a few decades ago.5International Journal of Epidemiology. US exceptionalism? International trends in midlife mortality
This matters for placing the US in the demographic transition model because the rising crude death rate is not simply a product of an aging population (the normal Stage 4 pattern). Some of it reflects genuinely elevated mortality among younger and middle-aged adults, a pattern that does not neatly fit any stage of the model. The demographic transition framework was built around long-run structural shifts in public health, not around a country developing a drug-poisoning epidemic while simultaneously maintaining a high rate of gun violence. The US is, in a sense, doing something the model never anticipated: progressing on fertility while partially regressing on mortality.
A Population That Is Graying Fast
Even setting mortality complications aside, the age structure of the US population tells a clear Stage 4 to Stage 5 story. The number of Americans aged 65 and older is projected to grow from about 58 million in 2022 to 82 million by 2050, a 42 percent jump. By that point, roughly one in four Americans will be 65 or older, up from about one in six today.6Population Reference Bureau (PRB). Aging in the United States The national median age has already risen from 30.0 in 1980 to 38.9 in 2022, and a third of states now have a median age above 40, with Maine and New Hampshire topping the list.6Population Reference Bureau (PRB). Aging in the United States
This aging trend is the signature footprint of late Stage 4. When birth rates stay low for decades, the base of the population pyramid narrows while the top expands, because large earlier cohorts keep aging while smaller cohorts replace them below. In the US, the baby boomers represent a particularly large bulge working its way through the upper end of the age distribution. As they enter their 70s and 80s, the crude death rate will rise further simply because more people will be at ages where death is common, independent of whether health care improves or deteriorates.
This creates a structural drag on the birth-to-death ratio. Even if fertility held perfectly steady, the number of deaths would climb for years as the population ages, narrowing the gap between births and deaths. Combine that with fertility that is already below replacement and you have the arithmetic of Stage 5 approaching on autopilot.
Not One Country but Many Transitions
The national averages mask enormous internal variation. Different racial and ethnic groups, different regions, and different immigration populations are each on somewhat different demographic trajectories. During the COVID-19 pandemic, for instance, life expectancy fell more steeply among all foreign-born subgroups than among their US-born counterparts, with foreign-born Hispanic men experiencing both the sharpest decline between 2017-2019 and 2020 and the slowest recovery by 2022.7PubMed Central. US-born and foreign-born life expectancy by race and Hispanic origin before and during the COVID-19 pandemic in the United States
Geography matters just as much. States in the Northeast and upper Midwest tend to have older populations, lower birth rates, and demographic profiles that resemble Stage 5 countries. States in the South and parts of the Mountain West often have younger populations, higher fertility, and profiles that look more solidly Stage 4. Utah, with its comparatively high birth rate, is a different demographic world from Maine, where deaths have been outpacing births for years. If you applied the demographic transition model at the state level, you would find a patchwork stretching across two or even three stages.
Immigration adds another layer. The US has historically relied on immigration to offset low native-born fertility, and immigrants tend to be younger and to have slightly higher fertility in their first years after arrival. Without immigration, the US population would already be approaching outright decline. With it, total population growth remains positive, though it has slowed considerably. Whether the country tips into Stage 5 at the national level depends heavily on immigration policy and flows over the next decade or two, a factor the classic demographic transition model does not really account for because it was designed to describe closed populations moving through industrialization.
Can Pro-Natalist Policy Change the Trajectory?
Several countries further along the Stage 5 path, including Japan, South Korea, and much of Southern and Eastern Europe, have launched aggressive pro-natalist policies to try to reverse their fertility declines. A large review of these policies across multiple countries found that cash-based benefits like child allowances, paid parental leave, and birth payments were both the most common and among the most effective approaches for nudging fertility rates upward.8PubMed Central. Reversing fertility decline in Japan with foreign pro-natalist policies, 1990–2035: a systematic review and secondary data analysis Other measures that showed promise included childcare coverage, tax exemptions, and insurance coverage for assisted reproductive technology.8PubMed Central. Reversing fertility decline in Japan with foreign pro-natalist policies, 1990–2035: a systematic review and secondary data analysis
The US has relatively few explicit pro-natalist policies by the standards of other wealthy countries. There is no universal paid parental leave at the federal level, childcare subsidies are limited and means-tested, and the child tax credit, while expanded temporarily during the pandemic, returned to its lower baseline. Some states have introduced their own programs, but nothing approaching the scale of what countries like France, Sweden, or Hungary have implemented. Whether the US adopts such policies is a political question more than a demographic one, but the international evidence suggests that generous family support can slow a fertility decline even if it rarely reverses one entirely. No country has managed to push fertility back up to replacement level through policy alone once it has fallen significantly below it.
Automation and the Dependency Question
One of the practical consequences of sitting at the edge of Stage 5 is a shifting dependency ratio, the balance between working-age adults who generate economic output and the older and younger populations who depend on that output. As the population ages and the workforce shrinks relative to retirees, the fiscal math behind Social Security, Medicare, and other transfer programs gets harder. Aging economies face mounting pressure from shrinking workforces and rising dependency ratios, a dynamic the US is increasingly feeling.9Critical Economic Implications of Global Demographic Changes. Economic Impact of Demographic Shifts Amid Labor Automation and Policy Inertia
Automation and artificial intelligence are frequently discussed as a potential offset: if machines can do more of the work, maybe fewer workers can support more retirees. Some researchers are exploring how rising robot density interacts with shifting age structures to reshape labor markets and productivity.9Critical Economic Implications of Global Demographic Changes. Economic Impact of Demographic Shifts Amid Labor Automation and Policy Inertia Japan, the country furthest along the aging curve among large economies, has invested heavily in automation and robotics partly as a demographic strategy. Whether this works as a substitute for a larger labor force remains genuinely uncertain. Productivity gains from technology could ease the burden, but they also tend to concentrate gains among those who own the technology, potentially widening inequality even as they address the raw labor shortage.
Does the Model Still Fit?
The demographic transition model was developed in the mid-twentieth century primarily by observing European countries and their former colonies. It assumes a fairly linear progression driven by industrialization, urbanization, and public health improvements. The US broadly followed that arc, but several features of its current situation strain the framework. The mortality anomaly among working-age adults does not fit any stage cleanly. The role of immigration as a population growth engine is not built into the model. And the sharp internal variation by state, race, and nativity means that the “US” stage designation is really an average of divergent local realities.
Still, the model is useful as a rough compass. The US has low birth rates, relatively low (though rising) death rates, a narrowing gap between births and deaths, and a rapidly aging population. By any reasonable reading of the framework, it is in late Stage 4. Whether it crosses into Stage 5, meaning sustained natural population decline, depends on whether births fall further, whether the mortality anomalies persist, and whether immigration continues to make up the difference. The most honest answer is that the country is straddling the line, not because the data is ambiguous but because Stage 4 and Stage 5 blend into each other when fertility sits just below replacement and the rest of the equation depends on external factors like immigration and opioid policy that the original model never contemplated.
How the US Compares with Other Late-Stage Countries
Among wealthy nations, the US is actually a relative latecomer to the Stage 5 threshold. Japan’s population has been shrinking since 2008. Germany’s native-born population has been in decline for decades, masked by immigration. South Korea now has the lowest fertility rate among major economies, well below one child per woman. Italy, Spain, and Greece have all seen their populations peak and begin to contract.
The US stands apart from these countries for two reasons. First, its immigration levels have historically been higher, adding younger people to the population in a way that delays the crossover point. Second, and more unusually, its death rate trajectory is worse than its peers, not because of aging but because of preventable deaths among younger adults. Most Stage 4 and Stage 5 countries see their crude death rates rise only because their populations are getting older. The US has that too, but it also has excess mortality from causes that other wealthy countries have largely brought under control. The result is a strange hybrid: a country that resembles Japan or Germany on the fertility side but looks more like a middle-income country on certain mortality metrics, arriving at the Stage 5 doorstep by a different and less orderly route than the textbooks describe.