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State Municipal Index • IL
Illinois Property Tax Drift Index
State Avg Drift Score
64/100
Illinois Municipal Risk Briefing
State Comptroller & US Census Bureau (IL)August 2026
Illinois maintains an average TaxDrift Score of 64/100 across monitored jurisdictions. Overlapping municipal bond issuances and assessment equalization rollbacks determine local millage carrying costs under statutory rules.
Population
12,549,689
Avg Effective Tax Rate
2.4%
Total Tracked Muni Debt
$91.3B
Counties Monitored
6
Statutory Tax Caps & Voter-Approval Rules (IL)
Property Tax Extension Limitation Law (PTELL) restricts non-home-rule taxing district increases to 5% or CPI.
Audited Counties in Illinois
Illinois County Tax Drift Leaderboard
6 Jurisdictions Audited| Rank | Jurisdiction | Drift Score | Risk Tier | Muni Debt / Cap | CAD Lag Spread | 3-Yr Tax Shock | Audit |
|---|---|---|---|---|---|---|---|
| #1 | Cook County, IL | 86.4 | Severe | $12,400 | +31.4% | +$3,053/yr | View |
| #2 | Lake County, IL | 65.7 | Elevated | $9,400 | +23.8% | +$2,852/yr | View |
| #3 | Kane County, IL | 58.9 | Elevated | $8,200 | +20.8% | +$2,140/yr | View |
| #4 | Will County, IL | 58.7 | Elevated | $8,400 | +21.0% | +$2,112/yr | View |
| #5 | DuPage County, IL | 58.3 | Elevated | $8,600 | +21.5% | +$2,387/yr | View |
| #6 | McHenry County, IL | 54.9 | Elevated | $7,900 | +19.5% | +$2,006/yr | View |