Build Philly Now · March 2026
The Mixed-Income Neighborhoods Overlay: A Parcel-Level Impact Analysis
Philadelphia’s MIN overlay imposed an unfunded 20% affordability mandate on new housing development of 10 or more units. Three and a half years later, the policy has produced 18 affordable units. Meanwhile, an estimated ~3,000 housing units that would otherwise have been built — including ~600 affordable units that would have been required under MIN’s own 20% set-aside — were never constructed.
What Is the MIN Overlay?
The Mixed-Income Neighborhoods (/MIN) overlay requires any residential development of 10 or more units to set aside 20% of units as affordable at 40% of Area Median Income — with no public subsidy to offset the cost. It took effect July 18, 2022 in portions of Council Districts 3 and 7.
The policy’s design flaw is not the goal of mixed-income neighborhoods. It is the expectation that private developers will absorb the full cost of below-market units with no public contribution. At 40% of Area Median Income (AMI) and current construction costs, the gap between market rents and affordable rents makes the math impossible for most projects. The result is predictable and now empirically demonstrated: developers don’t build.
The core finding
New construction of 10+ unit buildings inside MIN declined at an annualized rate of 37 percentage points more than the control group — from 27.7 permits/year to 8.7/year inside MIN, versus 6.8/year to 4.6/year outside. The 31.6% decline outside MIN captures market-wide headwinds (interest rates, construction costs, tax abatement changes). The additional 37 points inside MIN is the overlay’s measured impact, isolated from everything else affecting the market.
Explore the Analysis
The Evidence
Difference-in-differences methodology, quarterly trends, district breakdown, developer activity shift
Near Transit
How MIN destroyed near-transit development — and why the existing TOD overlay didn't help
Peer Cities
Portland funded it. Baltimore failed. Chicago leaks. Oregon banned unfunded IZ entirely.
Solutions
Fund it or kill it: four evidence-based recommendations to fix MIN and unlock housing
The Bottom Line
MIN’s unfunded affordability mandate has coincided with a 56.6% decline in housing unit production inside the overlay. The pre-MIN rate of 2,133 units per year from large projects fell to 926 per year. The policy has delivered 18 affordable units while an estimated ~600 that would have been required under its own 20% set-aside were never built. The goal of mixed-income neighborhoods is sound. The mechanism needs to change. Other cities have found better approaches, and Philadelphia can too.