Fact check: What were the population shifts that led to Illinois losing a congressional seat in 2020?

1. Summary of the results

Illinois lost a congressional seat following the 2020 Census due to a population decline of 0.1% to 0.14% between 2010 and 2020, with the state losing approximately 18,124 people over the decade ^{[1] [2] [3]}. This marked the first population decline in Illinois' 200-year history ^[2].

The population shifts that led to this loss were driven by several key factors:

• Domestic outmigration: People left Illinois for better housing and employment opportunities in other states ^[2]
• Educational migration: College students increasingly chose to attend out-of-state universities ^[3]
• Working-age and retiring population exodus: Both demographics left the state in significant numbers ^[3]
• High taxes: This was identified as the number one reason why Illinoisans consider leaving the state ^[4]

The population decline continued after 2020, with Illinois losing nearly 89,000 people since 2020 ^[5], and 84% of Illinois communities experiencing population loss ^[4]. Chicago alone lost nearly 30,000 residents ^[4].

2. Missing context/alternative viewpoints

The analyses reveal several important demographic trends not captured in the original question:

• Age-specific population shifts: Illinois is losing people 18 and under at a faster rate than any other state, with a 6% decline in this age group over four years ^[6]. The state's population is growing older with fewer working-age people ^[6].
• Geographic distribution: While the state overall lost population, some counties actually gained residents. Specifically, 15 counties gained new residents between 2020-2024, even as the state lost 88,930 residents overall ^[7].
• Migration destinations: Illinois residents moved to specific states including Indiana, Florida, and Texas ^[7].
• Census data disputes: Illinois officials claimed the state gained approximately 46,400 individuals after requesting a review of Census Bureau data, potentially impacting the congressional seat loss calculation ^[8].

3. Potential misinformation/bias in the original statement

The original question itself does not contain misinformation, as it accurately assumes that Illinois lost a congressional seat due to population shifts. However, the question's framing focuses solely on the 2020 Census period, which could lead to incomplete understanding of the ongoing demographic crisis.

The Illinois Policy Institute appears frequently in the sources ^[4], and organizations with specific policy agendas may benefit from emphasizing the role of high taxes in population decline to support their advocacy for tax reform. Conversely, Illinois state officials would benefit from disputing the Census data ^[8] to minimize the appearance of policy failures and maintain political credibility.

The data consistently shows that the population decline was not a one-time event but part of an accelerating trend that continued well beyond 2020, suggesting the congressional seat loss was just the beginning of Illinois' demographic challenges.