Housing Glossary
Key terms and definitions used in housing data and policy.
AMI (Area Median Income)
The midpoint of a region's income distribution, calculated by HUD for each metro and county. A household earning the AMI earns more than half of local households and less than the other half. AMI is the basis for most affordable housing program eligibility — e.g., 'households at 60% AMI' means those earning 60% of the local median.
Cost Burden
A household that spends more than 30% of its gross income on housing costs (rent or mortgage plus utilities). This threshold, established by HUD, indicates that a household may have difficulty affording other necessities like food, healthcare, and transportation.
Severe Cost Burden
A household spending more than 50% of its gross income on housing costs. Severely cost-burdened households face acute financial stress and are at significantly higher risk of housing instability, food insecurity, and deferred medical care.
CHAS (Comprehensive Housing Affordability Strategy)
Special tabulations of Census ACS data prepared by HUD that cross-tabulate housing problems (cost burden, overcrowding, inadequate facilities) by income level, household type, and race/ethnicity. CHAS data is the primary source for measuring housing needs at the local level.
FMR (Fair Market Rent)
An estimate by HUD of the amount needed to rent a moderately-priced unit in a specific area. Set at the 40th percentile of gross rents for standard-quality units. FMRs determine Housing Choice Voucher payment standards and are published annually for every metro and county.
ELI (Extremely Low Income)
Households earning at or below 30% of the Area Median Income, or the federal poverty level, whichever is higher. ELI households face the most severe affordability challenges — 72% are severely cost-burdened, and only 1 in 4 eligible households receives federal rental assistance.
HCV (Housing Choice Voucher)
The federal government's primary rental assistance program (formerly known as Section 8 vouchers). HCVs subsidize rent in the private market, with tenants paying approximately 30% of income and the voucher covering the remainder up to a payment standard. Approximately 2.3 million households use HCVs.
Section 8
Common name for two federal rental assistance programs: the Housing Choice Voucher (tenant-based) program and the Project-Based Rental Assistance program. Named after Section 8 of the Housing Act of 1937. Together, these programs serve approximately 5 million households.
Public Housing
Federally funded, locally managed housing developments owned by Public Housing Authorities (PHAs). Approximately 960,000 units serve 1.9 million residents. Public housing has seen decades of disinvestment, with a deferred maintenance backlog exceeding $70 billion.
LIHTC (Low-Income Housing Tax Credit)
The largest source of affordable housing production in the United States. Created in 1986, LIHTC provides tax credits to developers who set aside a percentage of units for households at 50-60% of AMI. LIHTC has financed approximately 3.6 million affordable units since inception.
Inclusionary Zoning
A land use policy requiring or incentivizing developers to include a percentage of affordable units in new market-rate developments. Typically requires 10-20% of units at 50-80% AMI. Over 1,000 jurisdictions have some form of inclusionary policy.
Rent Control / Rent Stabilization
Policies that limit how much a landlord can increase rent, typically on an annual basis. Modern rent stabilization usually caps increases at CPI or CPI + a fixed percentage (e.g., 3-7%). Approximately 200 U.S. jurisdictions have some form of rent regulation, while 37 states preempt it.
Just-Cause Eviction
A tenant protection requiring landlords to have a legally recognized reason (cause) for eviction — such as nonpayment, lease violation, or owner move-in. Without just-cause protections, landlords in many states can decline to renew a lease for any reason.
De Minimis
In housing policy, refers to a threshold below which certain regulations or requirements do not apply. For example, some inclusionary zoning policies exempt developments below a de minimis size (e.g., fewer than 10 units).
HMDA (Home Mortgage Disclosure Act)
A federal law requiring most mortgage lenders to report detailed data on loan applications, including applicant race, income, loan amount, property location, and outcome (approved/denied). HMDA data is the primary tool for analyzing lending equity and detecting discrimination.
LTV (Loan-to-Value Ratio)
The ratio of a mortgage loan amount to the appraised value of the property. A home purchased for $400,000 with a $360,000 mortgage has an LTV of 90%. LTV above 80% typically requires private mortgage insurance (PMI).
DTI (Debt-to-Income Ratio)
The percentage of a borrower's gross monthly income that goes to debt payments. The 'front-end' DTI measures housing costs only (typically capped at 28%); the 'back-end' measures all debt including housing (typically capped at 36-43%).
HPI (House Price Index)
An index measuring changes in single-family home prices over time. The FHFA HPI, based on repeat sales of properties with conforming mortgages, is the most widely used measure of home price appreciation in the U.S.
ZHVI (Zillow Home Value Index)
Zillow's smoothed, seasonally adjusted measure of the typical home value in a given geography. ZHVI represents the value of a home at the 35th to 65th percentile of the distribution, providing a middle-market benchmark.
ZORI (Zillow Observed Rent Index)
Zillow's measure of the typical observed rent in a given geography. ZORI is calculated from listed and observed rents, smoothed and seasonally adjusted, providing a consistent measure of rental market conditions.
CoC (Continuum of Care)
HUD's program and planning framework for addressing homelessness at the local level. The approximately 400 CoCs across the U.S. coordinate homeless services, conduct the annual Point-in-Time count, and apply for federal homelessness funding.
PIT Count (Point-in-Time Count)
An annual count of sheltered and unsheltered people experiencing homelessness, conducted by each CoC on a single night in late January. The PIT count is the primary data source for measuring homelessness in the U.S., though it is widely acknowledged to undercount the true population.
Housing Wage
The hourly wage a full-time worker must earn to afford a rental unit at Fair Market Rent without spending more than 30% of income on housing. The national housing wage for a two-bedroom apartment is $28.58/hour as of 2025. Calculated annually by the National Low Income Housing Coalition.
Affordability Index
A composite measure of housing affordability that considers home prices or rents relative to local incomes. Various indices exist (NAR, NAHB, Zillow); OpenHousing's affordability score combines rent burden, price-to-income ratio, and wage-to-housing-cost metrics.
Housing Trust Fund
A dedicated source of public funding for affordable housing, usually at the state or local level. The National Housing Trust Fund, established in 2008, is a federal program funded by Fannie Mae and Freddie Mac contributions, dedicated to rental housing for extremely low-income households. State and local housing trust funds collectively commit over $4 billion annually.
ADU (Accessory Dwelling Unit)
A secondary housing unit on a single-family residential lot, such as a garage apartment, basement unit, or backyard cottage. ADUs increase housing supply without changing neighborhood character and provide income for homeowners.
Missing Middle Housing
Housing types between single-family homes and large apartment buildings: duplexes, triplexes, fourplexes, townhomes, and small apartment buildings. Once common in American cities, missing middle housing has been largely eliminated by single-family zoning.