1. The source field
We use the City of Chicago Building Permits dataset. Its PROCESSING_TIME field is defined as the number of days from APPLICATION_START_DATE to ISSUE_DATE. We do not recompute that field from contact or address data.
2. Records included
The current edition includes permits issued from January 1, 2021 through September 15, 2026. Records must have a community area and a processing time from 0 through 730 days. The current day is always excluded so a partially published day cannot distort the latest period.
3. What the percentiles mean
The median is the middle observed wait: half of issued permits were faster and half slower. The 75th percentile is a more cautious planning reference. The 90th percentile shows the long-wait edge without letting a handful of extreme cases dominate the answer.
4. Publication threshold
We publish community-area-by-type and ZIP-by-type reports only when at least 25 issued permits survive the validity checks. Small groups are kept out of the index because their apparent medians are too unstable for a useful comparison.
5. Geography
“Neighborhood” pages use Chicago’s 77 official community areas, not informal neighborhood boundaries. ZIP pages use the City’s computed ZIP boundary assignment and official ZIP-boundary lookup table. A small number of records without a usable ZIP assignment appear in community-area and citywide totals but not ZIP reports.
6. Limits
This is an analysis of permits that reached issuance. It does not include the time spent on applications that were abandoned or denied, and it does not separate City review time from applicant response time. Permit type, review route, project complexity, corrections, and documentation quality can all affect elapsed time.