About the Index
The Center for Neighborhood Technology’s Housing and Transportation (H+T®) Affordability Index provides a more comprehensive way of thinking about the cost of housing and true affordability. The Index is the only tool of its kind that examines transportation costs at a neighborhood level. It allows users to view housing and transportation data as maps, charts, and statistics for nearly 900 metropolitan and micropolitan areas—covering 89 percent of the US population.
The Index shows that transportation costs vary between and within regions depending on neighborhood characteristics. People who live in location-efficient neighborhoods—compact, mixed use, and with convenient access to jobs, services, transit, and amenities—tend to have lower transportation costs. People who live in location inefficient places that require automobiles for most trips are more likely to have high transportation costs.
The traditional measure of affordability recommends that housing cost no more than 30 percent of income. Under this view, three out of four (76 percent) US neighborhoods are considered “affordable” to the typical household. However, that benchmark ignores transportation costs, which are typically a household’s second largest expenditure. The H+T Index offers an expanded view of affordability, one that combines housing and transportation costs and sets the benchmark at no more than 45 percent of household income. Under this view, the number of affordable neighborhoods drops to 28 percent, resulting in a net loss of 86,000 neighborhoods that Americans can truly afford.
The H+T Index data have implications for consumers, planners, and policy makers. [The Applications page of the website has more information about how the data can and has been used across the country.]
Throughout the evolution of the H+T Index model, described in detail to the right, the key finding remains the same: household transportation costs are highly correlated with urban environment characteristics, when controlling for household characteristics.
The H+T Index was developed by CNT and its partner, the Center for Transit Oriented Development (CTOD), as a project of the Brookings Institution's Urban Markets Initiative.
The first phase was released in January 2006 and specifically examined the variables that inform housing and transportation costs in St. Paul-Minneapolis, Minnesota. The key finding of this report is that location matters, and it can affect the true cost of housing when transportation costs are factored in. For more information see The Affordability Index: A New Tool for Measuring the True Affordability of a Housing Choice.
The initial H+T Index research found that two primary independent variables in the household transportation model—residential density and household income—drive three primary dependent variables: auto ownership, auto use and transit ridership. The Methods document fully explains the H+T Index methodology.
The initial Index received much attention from policy makers for its benefits to planners and transit-oriented development (TOD) advocates, and it served as the basis for several additional research projects.
In 2006 the Center for Housing Policy published A Heavy Load: The Combined Housing and Transportation Burdens of Working Families using H+T Index data compiled by CNT for working families in 28 metros.
In early 2008, CNT expanded the H+T Index to include neighborhood-level data for 52 US metropolitan areas, again with support from the Brookings Institution. This effort resulted in an interactive mapping website where users could see H+T Index results at the neighborhood level, with additional information on auto ownership, transit use, housing density, and other community characteristics. Also in 2008, CNT co-authored Estimating Transportation Costs by Characteristics of Neighborhood and Household, published by the Transportation Research Record: Journal of the Transportation Research Board.
At the height of the gasoline price peaks in the summer of 2008, CNT added maps for the 52 metros on the H+T Index website, showing how rising gasoline prices adversely affected vulnerable auto-dependent neighborhoods.
In 2009, in partnership with the Urban Land Institute's Terwilliger Center for Workforce Housing and the Center for Housing Policy (CHP), CNT produced an updated H+T Index analysis for the Washington, D.C. area, culminating in Beltway Burden: The Combined Cost of Housing and Transportation in the Greater Washington, DC, Metropolitan Area. To expand the reach of the H+T Index, CNT developed a new online housing and transportation cost calculator where consumers can access up-to-date Washington, D.C. cost data to make informed housing decisions. CNT later partnered with ULI and CHP to produce Bay Area Burden: Examining the Impacts and Hidden Costs of Housing and Transportation and added the San Francisco region to the online cost calculator.
In 2009, a new greenhouse gas analysis was included on the website, providing two views of urban greenhouse gas emissions associated with household auto use.
In March 2010, CNT expanded the Index to 337 metros in the United States, providing coverage for more than 80 percent of the US population.
CNT thanks its funders for their insightful and generous support for the development and expansion of the H+T Index: The Brookings Urban Markets Initiative, Center for Housing Policy of the National Housing Conference, Nathan Cummings Foundation, The Energy Foundation, Field Foundation of Illinois, The Ford Foundation, Lloyd A. Fry Foundation, Grand Victoria Foundation, The Joyce Foundation, John D. and Catherine T. MacArthur Foundation, McKnight Foundation, Rockefeller Foundation, Searle Funds at the Chicago Community Trust, Surdna Foundation, U.S. Department of Housing and Urban Development, and Wallace Global Fund.