Illinois Is Losing Young People Faster Than the Rest of the Country, Census Data Shows

Illinois is losing its young people faster than almost anywhere else in the country. New population estimates from the U.S. Census Bureau show that the state's under-20 population has fallen about 7 percent since July 2020, more than three times the roughly 2 percent decline for the United States as a whole. The national youth population is shrinking too, as birth rates fall and the population ages, but Illinois is dropping at a much sharper rate.

The gap runs through the working-age groups as well. An analysis of the data by Bryce Hill of the Illinois Policy Institute found that adults in their 20s, 30s, and 40s grew between 4.3 and 5.5 percent nationally over the past five years, while the same groups in Illinois grew just 1.2 percent or less.

Not just births and aging

What makes the Illinois numbers stand out, Hill argues, is that they cannot be chalked up to natural demographic change alone. "We have very similar birth rates, we have a similar median age, we have a similar age distribution as the rest of the nation," he said. "However, the population trends are working against Illinois." His conclusion is that the difference comes down to people leaving the state.

Illinois is one of the states losing population overall, a trend visible on the fastest-shrinking states ranking, and the youth decline is the leading edge of it. When young families and young workers move out, the effect shows up first and hardest at the bottom of the age pyramid.

The tax argument

The Illinois Policy Institute, a group that advocates for lower taxes and smaller government, ties the outmigration largely to the state's tax burden, and points to earlier reporting on why residents leave. According to the Tax Foundation, Illinois ranked 10th highest in the nation for state and local tax collection per capita in fiscal 2023. All five states bordering Illinois fell in the bottom half of that same ranking, and Hill notes that several of the state's major population centers sit close to those borders, making a move across a state line an easy one.

That interpretation comes from a group with a clear point of view, and demographers generally caution that migration has many causes, including jobs, housing, and family. What the Census data itself shows is narrower and not in dispute: Illinois is shedding young residents far faster than the country as a whole.

Why it matters

The consequences Hill describes are fiscal. Fewer young residents means fewer future taxpayers to carry the state's large fixed costs, most notably its unfunded pension liabilities, which he put at roughly $140 billion. A shrinking pipeline of young workers can also make it harder for employers to fill jobs and, he warns, could discourage new investment. Whatever the cause, an age structure that keeps tilting older is a harder one to build a budget on.

You can explore the population and age profile of Illinois and compare it against any other state with the compare tool, see where the country's youngest places are on the youngest cities ranking, or read where the national population is headed in our post on the U.S. population in 2050.

Sources

Reporting and the analysis quotes are from The Center Square, drawing on work by Bryce Hill of the Illinois Policy Institute. The underlying figures are from the U.S. Census Bureau's Vintage 2025 population estimates, and the tax ranking is from the Tax Foundation.