The Village of Oak Park board has identified housing affordability as a key economic benefit of eliminating single-family zoning across Oak Park neighborhoods. A common U.S. benchmark classifies housing as affordable when total housing costs (rent/mortgage payments, property taxes, insurance) do not exceed 30% of Area Median Income (AMI).
The board premises that adding more “middle housing” advances affordability, using a basic economic argument that increasing housing supply makes housing affordable.
The S.B. Friedman Financial Feasibility Study estimates large feasibility gaps for all new middle-housing types, drawing the obvious conclusion that new middle housing faces substantial financial feasibility hurdles, even at relatively high market rents – i.e. they do not meet the criteria for affordability.
The board argues while it’s obvious that new construction is unaffordable, new construction makes existing housing affordable in the long-term.
The cited example is that Oak Park added approximately 1,750 market-rate rental units from 2013 to 2023. The Illinois Housing Development Authority (IHDA) count of affordable-housing units increased by 1,350 unit during those 10 years. This is intended to demonstrate that construction of new market-rate housing in Oak Park directly resulted in the “creation” of substantial numbers of affordable units through migration-chains (households moving from cheaper to more expensive housing, making cheaper housing available to lower-income households), and filtering (process where new housing makes older housing cheaper).
However, examination and reconstruction of the 2013 vs. 2023 IHDA analysis reveals:
1. Though new constructions were rental apartments, the actual number of affordable renter-occupied units decreased by 8.
2. The number of affordable owner-occupied units increased by 1,358. This increase is primarily driven by IHDA input assumptions:
a. IHDA used higher Median Household Income ($61,045 in 2013 vs. $78,790 in 2023).
b. IHDA used a lower benchmark Mortgage Interest Rate (4.8% in 2013 vs. 3.98% in 2023).
c. The result is a higher “affordable purchase price” of $171,483 in 2023 vs. $123,145 in 2013, making more owner-occupied housing units affordable within the IHDA analysis – not the new apartment construction.
Economist Evan Mast (2019) researched 12 large U.S. metropolitan areas and found that new market-rate construction does reach lower-income neighborhoods over time, through migration chains that operate across large metropolitan areas to create affordable housing across the entire area. He does not establish that those migration chains can be contained within a small village of 4.7 sq. miles with ~55,000 people and ~22,000 households; therefore, it cannot be used to demonstrate that 1,750 market-rate apartments constructed inside Oak Park caused 1,350 other units inside Oak Park to become affordable. This is evident in the numbers above.
Common sense dictates housing markets do not stop at village borders. For example, a household moving into a new Oak Park apartment may come from Chicago. The replacement household may come from Rogers Park; the next vacancy may occur in Berwyn. This scenario is consistent with Mast’s research but creates a net-zero affordable housing gain inside Oak Park.
Further research such as Bratu, Harjunen and Saarimaa’s study of moving chains in the Helsinki metropolitan area establish the same result but explicitly conclude that new supply is likely to improve affordability outside the sub-markets where new construction occurs.
Housing prices reflect supply, demand and costs (land, construction, taxes, etc.) – not supply alone. Increasing supply can put downward pressure on prices, but that is different from suggesting that Shape Oak Park will make housing cheaper or affordable in the short-term or long-term.
Sources:
1. Shape Oak Park Financial Feasibility Study (9/18/2026)
2. 10 bad arguments against housing reform (Josh VanderBerg, Wednesday Journal, 4/7/2026)
3. The Affordability Engine (Josh VanderBerg, Wednesday Journal, 7/24/2026)
4. Affordable Housing Planning and Appeal Act (AHPPA) 2023 Non-Exempt Local Government Handbook, Illinois Housing Development Authority
5. The Effect of New Market-Rate Housing Construction on the Low-Income Housing Market (Evan Mast, W.E. Upjohn Institute for Employment Research, 7/1/2019)
6. City-wide Effects of New Housing Supply: Evidence from Moving Chains, (VATT Institute for Economic Research Working Papers by Cristina Bratu, Oskari Harjunen and Tuukka Saarimaa, 9/24/2021)
Rohan Fernandes is a finance professional, and resident of Oak Park for 8.5 years.
