The Evidence
11,431 building permits analyzed. 3.54 years before MIN, 3.45 years after. A 37-point collapse in new housing construction that can't be explained by the market alone.
Difference-in-Differences Design
This analysis compares building permits inside the MIN overlay to permits outside MIN but within the same council districts (CD3 and CD7). This within-district design controls for neighborhood-level trends, political attention, demographics, and market cycles. The only systematic difference between the two groups is MIN exposure.
Because the pre-MIN period (3.54 years) and post-MIN period (3.45 years) differ slightly in length, annualized rates provide a fairer comparison than raw counts. Only permits with confirmed unit counts of 10 or more are included — these are the projects MIN legally regulates.
| Pre-MIN | Post-MIN | Change | |
|---|---|---|---|
| Inside MIN | 27.7/yr | 8.7/yr | −68.6% |
| Outside MIN (control) | 6.8/yr | 4.6/yr | −31.6% |
| MIN effect (DiD) | −37 percentage points |
| Pre-MIN | Post-MIN | Change | |
|---|---|---|---|
| Inside MIN | 35.3/yr | 16.8/yr | −52.4% |
| Outside MIN (control) | 10.5/yr | 7.8/yr | −25.1% |
| MIN effect (DiD) | −27.3 percentage points |
Why two tables?
The first table (−37 percentage points)isolates new ground-up construction — the strongest causal claim, since these projects face MIN’s full economic burden. The second table (−27.3 percentage points)includes all permit types; the smaller effect reflects that addition/alteration projects actually increased slightly inside MIN, as some developers shifted to smaller conversions that stay below the 10-unit trigger. The 31.6% decline in the control group captures market-wide headwinds that affected all of Philadelphia — not just MIN zones.
Large Residential Permits Over Time
Quarterly count of 10+ unit building permits, inside vs. outside the MIN overlay. Key policy events annotated.
Original Dec 31, 2020 deadline for 100% 10-year tax abatement applications. Extended to 2021 due to COVID.
June 24, 2021 — CMs Gauthier and Quiñones Sánchez introduce the Mixed Income Neighborhoods Overlay Bill.
Dec 31, 2021 — Extended abatement deadline. Developers flood L&I with permits. Dec 16 — MIN bill receives final Council approval (Bill 220519).
Jan 1, 2022 — Tax abatement reduced to 10%/year phase-down. 1% construction tax imposed on all new permits.
July 18, 2022 — MIN overlay becomes effective. 20% affordability mandate at 40% AMI on 10+ unit projects, no public subsidy.
May 2022 — Bill 220452 designates 52nd, 56th, 60th, 63rd St as TOD stations. Affordable Housing Preservation overlay (AHP) also passes.
Jan 2023 — CMs Gauthier and Jones introduce bill to add Market St (54th–63rd) and surrounding blocks to MIN overlay.
Dec 2024 — Bill to expand MIN into Buckius St and Tioga St areas (Kensington/Northeast portions).
Cumulative Housing Units: The Widening Gap
Running total of housing units from large projects (10+ units). The inside-MIN line flattens after the policy takes effect.
How Many Housing Units Were Lost?
All methods use a 0% growth counterfactual — flat continuation of the pre-MIN rate, with no assumed market growth. This is deliberately conservative.
64 fewer large permits were filed inside MIN than expected under a flat (0% growth) continuation of the pre-MIN rate. The number of lost housing units depends on the average project size. Because the distribution of project sizes is skewed — a few very large projects pull the average up — we present three estimators for transparency:
| Estimator | Avg Units/Permit | Estimated Lost Units | Lost Affordable (20%) |
|---|---|---|---|
| Mean | 60.4 | 3,866 | 773 |
| Trimmed mean (5th–95th percentile) | 46.6 | 2,983 | 597 |
| Median | 30.0 | 1,920 | 384 |
The trimmed mean excludes the largest and smallest 5% of projects to reduce the influence of a few mega-projects (26 projects over 100 units, max 405). The median (30 units) represents the typical project. We use the trimmed mean (~3,000 units) as the headline estimate.
District Breakdown: CD7 Was Hit Hardest
| Metric | CD3 Inside | CD3 Outside | CD7 Inside | CD7 Outside |
|---|---|---|---|---|
| All permits | -21.7% | -6.2% | -45.5% | +23.5% |
| Large projects (10+u) | -50.8% | 0% | -66.7% | -71.4% |
| Entity/Developer permits | -43.8% | −13.7% | -51.9% | −3.5% |
CD7 shows the starkest divergence: overall permits inside MIN dropped 45.5% while growing 23.5% outside.
| District | Pre-MIN | Post-MIN | Decline |
|---|---|---|---|
| CD3 (Gauthier) | 3,455 units | 324 units | −91% |
| CD7 (Lozada) | 2,750 units | 559 units | −80% |
Large Permits by District
Hot Submarket Differential: 78.9 Percentage Points
Addresses with 3+ total permits over the study period — the most actively developed sites — show the most extreme divergence.
| Inside MIN | Outside MIN | Differential | |
|---|---|---|---|
| Combined | -28.3% | +50.6% | 78.9 percentage points |
| CD3 | -16% | +53% | 69 percentage points |
| CD7 | -61.2% | +49% | 110.2 percentage points |
110-point swing in CD7
In District 7, active development sites inside MIN collapsed 61.2% while equivalent sites outside MIN surged 49%. Builders didn’t leave the neighborhood — they left the overlay.
Developer Activity Flipped
Entity and developer permits inside MIN fell 47.7% while falling only 10.7% outside — a 37 percentage point differential. Only 16 specific developers (2.4% of those active inside MIN pre-policy) were identified building outside MIN post-policy. The effect is less “flight” and more “freeze.”
Every Zoning Category Collapsed
| Zoning | Pre-MIN | Post-MIN | Change |
|---|---|---|---|
| CMX-2.5 | 19 | 3 | -84% |
| CMX-2 | 22 | 7 | -68% |
| CMX-3 | 8 | 2 | -75% |
| CMX-4 | 10 | 4 | -60% |
| CMX-5 | 3 | 0 | -100% |
| IRMX | 15 | 5 | -67% |
IRMX — specifically designed to encourage industrial-to-residential conversion — collapsed 67%. The city upzoned these parcels for density, and MIN made the upzoning uneconomic.
No Evidence of 9-Unit Threshold Gaming
Are developers downsizing projects to exactly 9 units to stay below MIN’s 10-unit trigger? No. Post-MIN inside MIN, there were only 4 nine-unit projects and 5 eight-unit projects. The ratio of just-under (7–9 unit) to just-over (10–12 unit) projects actually declined from 2.28 pre-MIN to 1.08 post-MIN.
No evidence of threshold gaming. Developers are not downsizing — they are simply not building.
Developers are not strategically downsizing to avoid the mandate. They are simply choosing not to build in MIN zones at all.
The Highest-Value Parcels Stopped Developing
| Characteristic | Pre-MIN | Post-MIN |
|---|---|---|
| Median lot size | 9,652 sqft | 7,922 sqft |
| Median market value | $3,749,050 | $1,598,000 |
| Entity/Developer share | 79% | 69% |
| Individual share | 5% | 20% |
Post-MIN large projects skew toward smaller lots and lower-value properties, suggesting only marginal projects proceed. The highest-value parcels — the ones most likely to produce significant housing — stopped developing entirely.