Projecting the long-term effects of the COVID-19 pandemic on U.S. population structure

The COVID-19 pandemic disrupted key demographic processes in the United States—mortality, fertility, and migration—in ways that directly and indirectly altered population size and structure. From early 2020 through December 2022, 1.07 million COVID-19 deaths were recorded in the U.S., with excess deaths estimated at 1.23 million, contributing to a 2.7-year decline in life expectancy at birth between 2019 and 2021. Fertility declined by 4% from 2019 to 2020 (TFR 1.71 to 1.64), with a partial rebound to 1.66 in 2021. Net international migration fell sharply (to an estimated 376,000 between July 2020 and June 2021), around half the level of the prior year and 70% below the decade’s peak, driven in part by the enactment of Title 42 and travel restrictions. While these shifts have been documented separately, less is known about how their joint disruption has reshaped overall population counts and future age structure. The study’s objective is to quantify how pandemic-era changes in mortality, fertility, and migration jointly affected the U.S. population and to project the lasting effects on size, age-sex distribution, and dependency ratios through 2060 by comparing a baseline (with COVID-19) scenario to a counterfactual (without COVID-19). The work underscores the importance of integrated demographic modeling for planning related to health care, education, housing, and public finance.

Prior work has largely examined mortality, fertility, and migration changes in isolation during the pandemic, noting substantial mortality shocks (including excess mortality and declines in life expectancy), short-term fertility fluctuations (a 2020 ‘baby bust’ followed by a modest 2021 ‘baby bump’), and severe disruptions to migration due to Title 42 and travel restrictions. Few studies have assessed joint effects on population structure; exceptions include González-Leonardo and Spijker (2022) for Spain and Wilson et al. (2022) for Australia, which similarly emphasize persistent demographic ripples. The paper also situates dependency ratios as standard summary indicators for economic implications of demographic change, referencing established literature on population change and economic outcomes. Additionally, it notes social patterning of mortality by race/ethnicity in the U.S. and policy-driven migration shifts (e.g., Title 42, earlier refugee policy changes), contextualizing the U.S. experience within broader demographic and policy research.

Design: Two-sex cohort component population projection starting from the U.S. population on 1 January 2020, projecting annually to 2060 by age (0–100+) and sex. Inputs include age-sex-specific mortality rates and migration counts, age-specific fertility rates (for females), and sex ratios at birth. Data sources: United Nations World Population Prospects (UNWPP) 2022 forecasts for the United States (compiled from U.S. Census Bureau, Vital Registration, and international estimates). Scenarios: - Baseline (with COVID-19): UNWPP 2022 medium scenario forecasts for mortality, fertility, and migration. - Counterfactual (without COVID-19): constructed to remove pandemic-era shocks and align with expected pre-pandemic trajectories: • Mortality: For 2020–2024, derive counterfactual age-sex-specific mortality by linearly interpolating log mortality rates between 2019 and 2025, then exponentiating. • Fertility: UNWPP assumes no long-term fertility impact; construct counterfactual age-specific fertility only for 2020 by averaging baseline TFR in 2019 and 2021 and applying the 2021 age-specific fertility pattern. • Migration: Assume return to pre-pandemic trajectory in 2022; obtain counterfactual total net migration counts for 2020–2021 by linear interpolation between 2019 and 2022 baseline totals. Distribute totals across age and sex using Rogers–Castro model migration schedules (family model) implemented via the R package DemoTools. Modeling approach: - Stochastic projections with 1,000 iterations. Mortality is modeled as binomial survival (n = age-specific population, p = survival probability). Births are modeled as Poisson counts with mean equal to the deterministically implied births from age-specific fertility rates. - Outputs: For each year, compute absolute and relative differences between baseline and counterfactual populations by age and sex (the ‘missing population’ due to the pandemic). - Decomposition: Because standard cohort component projections do not decompose contributions by component, run three additional counterfactual variants holding two components at baseline and setting only one (mortality, fertility, or migration) to counterfactual values to approximate component-specific impacts. - Dependency ratios: Calculate young-age (<15/15–64), old-age (≥65/15–64), and total dependency ratios ((<15 + ≥65)/15–64) for baseline and counterfactual scenarios; report absolute differences. Assumptions: Following UNWPP, mortality, fertility, and migration return to pre-pandemic trajectories within a few years. Analyses end in 2060 due to growing uncertainty thereafter. Replication materials (data and R scripts, R 4.2.2) are provided via OSF.

- Overall population impact: In the absence of the pandemic, the U.S. would have 2.1 million (0.63%) more people in 2025 and 1.7 million (0.44%) more people in 2060 than the UNWPP baseline (with COVID-19). The absolute short-term loss is largest among ages 15–49 and greater for males than females; the largest relative short-term reduction is among ages 85+ (≈3.5% males, 2.0% females). By 2060, relative losses converge near 0.4% across age groups under 85. - Persistence and reverberation: Changes induced by the pandemic persist for decades, with cyclical reverberations across cohorts due to fewer reproductive-aged individuals and fewer births. For the 2020 birth cohort, there are over 42,000 (2.34%) fewer females and 44,000 (2.33%) fewer males in 2025 than in the no-pandemic counterfactual. - Component-specific contributions (2040 illustration): • Mortality shocks concentrated at older ages (stronger for men). • Fertility dip in 2020 yields about 35,000 fewer females (1.87%) and 37,000 fewer males (1.88%) in the 2020 cohort by 2040. • Migration disruptions (e.g., Title 42) drive the largest long-term losses, especially among reproductive ages: ≈660,000 fewer people ages 15–49 (0.41%) and ≈220,000 fewer ages 50–64 (0.34%), with downstream effects via fewer future births. - Dependency ratios: The total dependency ratio is 0.16 percentage points lower in 2025 than without the pandemic, largely due to mortality’s reduction of the old-age dependency ratio; migration partially offsets this by increasing dependency ratios. Over time, the overall dependency ratio effect diminishes and turns slightly positive between 2040 and 2060. The combined effects modestly increase the shares of ages 0–14 and 15–49 by about 0.05 percentage points in 2025, indicating only minor reshuffling of age composition.

The study integrates pandemic-induced changes in mortality, fertility, and migration to assess their joint and lasting impacts on U.S. population size and structure. Contrary to a perception that effects would be confined to older ages, the projections show that demographic ripples remain visible in the population pyramid through at least 2060. Three insights stand out: (1) Migration disruptions during 2020–2021 produce the largest long-term reduction in population size, particularly among working and reproductive ages, exceeding the lasting effect of elevated mortality; (2) The number of reproductive-aged individuals (15–49) is projected to remain lower for decades, due to fewer migrants at childbearing ages, pandemic-related mortality in those ages, and second-order effects on births; and (3) High mortality among older adults slightly lowers the total dependency ratio in the near term, with this effect partially offset by migration shortfalls that tend to increase dependency. These findings underscore how policy responses (e.g., Title 42) can affect population dynamics through channels distinct from public health goals, with implications for labor supply, aging, and public finance. The results also highlight the importance of comprehensive demographic modeling to inform planning for healthcare, childcare, housing, and economic policy.

Pandemic-era disruptions to mortality, fertility, and migration jointly reshaped the U.S. population, with effects persisting to at least 2060. Among components, migration reductions impart the largest and most durable impact on population size, particularly at working and reproductive ages, while elevated mortality at older ages temporarily lowers dependency ratios. The study demonstrates the value of integrating co-occurring demographic shocks rather than analyzing processes in isolation. Future research should: (a) examine longer-term and indirect pandemic consequences (e.g., long COVID, unmet healthcare needs) on mortality and disability; (b) incorporate improved age- and sex-specific migration data and alternative migration schedules; (c) develop more nuanced dependency measures based on labor force participation and health status; (d) apply similar integrated projection frameworks to other crises (e.g., maternal health and midlife mortality crises, abortion policy changes, opioid epidemic) and to other countries to compare cross-national demographic impacts.

- Scenario and forecast uncertainty: Baseline (with COVID-19) relies on the UNWPP 2022 medium scenario; counterfactuals are constructed from the same forecasts, so results inherit forecasting uncertainty. Although differences between scenarios mitigate compounding errors, true no-pandemic rates cannot be observed. - Migration data and schedules: Limited age- and sex-specific migration counts necessitated use of model (Rogers–Castro) migration schedules and a ‘family’ pattern for both baseline and counterfactual scenarios. If actual pandemic-era declines differed by age/sex from assumed patterns, component-specific effects—especially second-order impacts via never-born children—may be misestimated. - Post-pandemic trajectory assumptions: Following UNWPP, mortality, fertility, and migration are assumed to return to pre-pandemic trajectories within a few years. If mortality remains elevated or fertility/migration remain depressed, impacts are underestimated. Indirect and longer-term effects (e.g., long COVID, unmet care, kin loss, learning loss, xenophobia) are not captured. - Dependency ratio simplicity: Dependency ratios are calculated using age thresholds rather than economic activity or health-adjusted measures; more nuanced projections of labor force participation and health by age are unavailable in UNWPP projections. - Temporal granularity: Lack of higher-frequency (monthly/weekly) migration and vital data limits analysis of short-term dynamics and timing effects.