Question 1

Where does this crime data come from?

Accepted Answer

Crime statistics come from Illinois's crime reporting program, which collects monthly offense data from local police departments using the FBI's National Incident-Based Reporting System (NIBRS). Data is reported by each agency and published through the state.

Question 2

What is the difference between Group A and Group B offenses?

Accepted Answer

Group A offenses are more serious crimes tracked in detail, including assault, burglary, theft, fraud, drug offenses, and weapons violations (22 categories total). Group B offenses include less serious crimes like DUI, disorderly conduct, trespass, and curfew violations, where only arrest data is collected.

Question 3

Why might crime numbers look different from other sources?

Accepted Answer

Different sources use different reporting standards. The FBI transitioned from Summary Reporting (UCR) to NIBRS in 2021, which counts incidents differently. Some agencies may also have reporting gaps or delays. Month-to-month comparisons within the same source are most reliable.

Question 4

How often is this data updated?

Accepted Answer

Crime statistics are refreshed weekly from the state reporting system. Monthly totals may take 30-60 days to finalize as agencies submit and correct their reports. The most recent month shown may have incomplete data.

Arlington Heights, IL

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