Inside the CBO Data: Why the US Population Will Shrink by 2033 Without Net Immigration

The mathematics of American population growth are undergoing a fundamental transition. For decades, the United States relied on a reliable engine of natural increase—more births than deaths—to expand its workforce, fuel consumer demand, and support an aging population. But that engine is stalling. According to the Congressional Budget Office's long-term demographic outlook, the U.S. is rapidly approaching a historic threshold.[1]

By 2033, the CBO projects that the annual number of deaths in the United States will exceed the annual number of births. It is a demographic crossover point that alters the trajectory of the nation. From that year forward, the natural growth rate of the U.S. population drops below zero, meaning that without net immigration, the country would begin to physically shrink.[1]

The data, detailed in the CBO's "The Demographic Outlook: 2025 to 2055," paints a picture of a nation aging into a new economic reality. The agency projects the total U.S. population will reach 372 million by 2055. While that represents an absolute increase, the pace of that growth is decelerating dramatically.[1]

Between 1975 and 2024, the U.S. population grew at an average rate of 0.9 percent per year. Over the next decade, that rate is expected to fall to 0.4 percent. By the period spanning 2036 to 2055, the growth rate will slow to a near-standstill of 0.1 percent annually—less than one-quarter of its historical average.[1]

The primary driver of this slowdown is a sustained collapse in the total fertility rate. To maintain a stable population without immigration, a country requires a replacement rate of roughly 2.1 births per woman. The U.S. has operated below that threshold for years, and the CBO model projects the decline will deepen.[1]

The agency forecasts that the fertility rate for women under the age of 30 will continue to fall, dropping from 0.79 births per woman in 2025 to just 0.62 by 2055. While the rate for women over 30 is expected to rise slightly as Americans delay childbearing, it is not enough to offset the broader contraction.[1]

This leaves immigration as the sole mechanism for long-term population expansion. The CBO notes that through 2032, net births will account for roughly one-sixth of projected population growth, with immigration accounting for the rest. But once the 2033 crossover hits, immigration will account for 100 percent of the nation's net growth.[1]

The stakes of this shift are highly visible in the labor market. The civilian noninstitutionalized population—the metric used to project the size of the workforce—is aging rapidly. The CBO projects that the number of Americans age 65 or older will grow at an average annual rate of 1.1 percent through 2055.[1]

In contrast, the prime working-age population, defined as adults between 25 and 54, will grow at a sluggish 0.3 percent per year. The youngest cohort of the workforce, those aged 16 to 24, is actually projected to decline on average over the next three decades.[1]

This growing imbalance between retirees and active workers places immense structural pressure on federal entitlement programs. Social Security and Medicare rely on current payroll taxes to fund current beneficiaries. As the ratio of workers to retirees shrinks, the mathematical burden on the remaining labor force intensifies.[1][3]

The national projections, however, mask deep regional disparities. The 2033 crossover point is a national average, but natural decrease is already a reality for vast swaths of the country. Data from the Population Reference Bureau reveals that the buffer provided by immigration is highly localized.[2]

Between 2024 and 2025, net international migration prevented population loss in just 254 U.S. counties. In another 882 counties, immigration helped offset losses but could not entirely erase them. Most starkly, 377 counties lost population despite gaining international migrants, underscoring how deeply entrenched the demographic decline has become in certain regions.[2]

For these shrinking counties, the economic consequences are immediate. A declining local population means a shrinking tax base, reduced consumer spending for local businesses, and a smaller pool of essential workers for healthcare, education, and infrastructure maintenance.[2][3]

The CBO acknowledges that its 30-year projections carry significant uncertainty. Small shifts in fertility behavior, mortality rates, or federal border policy compound over decades, leading to vastly different outcomes. The 2025 outlook, for instance, revised the 2055 population target down by 11 million people compared to the previous year's estimate, driven by updated census data and executive actions that temporarily reduced asylum processing.[1]

If immigration levels fall below the CBO's baseline assumptions, the onset of national population decline could arrive even sooner than 2033. Conversely, a sustained increase in net migration could delay the contraction and provide a larger prime-age workforce to support the aging Baby Boomer and Generation X cohorts.[1][3]

Ultimately, the data presents a clear mathematical boundary. The United States can no longer rely on natural birth rates to sustain its economic expansion. As the 2033 threshold approaches, the nation's demographic future—and the fiscal health of its institutions—will be determined entirely by its approach to immigration.[3]