WASHINGTON, D.C., MARCH 2, 2026 — Forty-two of the 50 largest U.S. housing markets are less affordable in 2024 than they were in 2018, according to the newly released Polygon Affordability Index (PAI), developed by Polygon Research.

Built entirely on loan-level data from the Home Mortgage Disclosure Act (HMDA), the Polygon Affordability Index measures housing affordability using actual originated mortgage transactions rather than survey-based estimates or modeled median household assumptions. The analysis applies a consistent methodology across 2018 and 2024 and focuses on purchase mortgages in the 50 largest U.S. mortgage markets.

Traditional affordability indexes use median assumptions. PAI captures the lived experience of real borrowers in actual transactions, in every community across the country. - Greg Oliven, Chief Technology Officer, Polygon Research

‍Among the findings:

• ‍Seattle ranks as the least affordable major housing market in the study. In 2024, monthly mortgage payments consume 26.6% of borrower income in Seattle, up from 20.8% in 2018. Seattle’s overall PAI score declined from 52.7 to 47.4, the lowest among the 50 markets analyzed.
• ‍Boise recorded the largest overall affordability decline. Its PAI score fell 8.5 points, from 61.4 in 2018 to 52.9 in 2024. Down payment burden increased from 61.5% to 87.2% of annual borrower income.
• ‍Mid-size Midwest markets experienced some of the steepest deterioration. Columbus, Cincinnati, Indianapolis, Kansas City, Louisville, and Milwaukee each recorded declines exceeding six points, reflecting significant reductions in borrower purchasing power since 2018.
• ‍Boston’s down payment burden reached 96.2% of annual borrower income in 2024, highlighting the growing savings barrier to homeownership even in markets where monthly payment measures may appear comparatively stable.
• ‍Los Angeles and San Francisco posted modest improvements in overall index scores, reflecting changes in borrower income relative to loan size among households transacting during the period studied.

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About the Polygon Affordability Index

The Polygon Affordability Index (PAI) is an interactive housing affordability measure built entirely on HMDA loan-level data. Markets are scored on a 0–100 scale, where higher values indicate greater affordability.

The index combines three components:

1) Payment Burden (50% weight)

Taking the available native HMDA data, monthly principal and interest payments are calculated as a percentage of borrower monthly income.

2) Price Burden (30% weight)

Price Burden is calculated as property value relative to annual borrower income.

3) Down Payment Burden (20% weight)

Down payment burden is the required down payment as a percentage of borrower annual income

The analysis includes fixed-rate, first-lien, closed-end purchase loans for 1–4 family primary residences that were originated during the study years. Transactions with reported property values or applicant incomes above $100 million are excluded to remove potential data-entry outliers.

Unlike traditional affordability indexes, which rely on survey estimates or median household modeling, PAI reflects the lived experience of borrowers based on actual mortgage transactions. The index is fully interactive within HMDAVision, Polygon Research’s mortgage market intelligence platform. Users can analyze affordability at national, state, metropolitan, county, and census tract levels and filter results by borrower income tier, age, race, ethnicity, and loan characteristics. Data coverage is consistent from 2018 forward.

Full 50-market ranking (sortable table): https://www.polygonresearch.com/affordability-index

A 90-second overview video introducing the index is available on YouTube.

A webinar replay is also available on demand.

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