Resources: Affordable Housing Baseline Estimate References
Reference data is available within this table (External Link) to assist local governments in understanding how an affordable housing baseline and annual goal can differ based on the income limit used to calculate that baseline. This data is not the local government affordable housing baselines of localities — these will be developed by local governments, not the State — but are rather to assist in the development of baselines and to inform the design of other resources.
The data used to create the baseline references are sourced from the U.S. Census Bureau American Community Survey, and the U.S. Department of Housing and Urban Development Comprehensive Housing Affordability Strategy. These sources are used to determine the estimated number of rental units at given gross rent range¹, ownership units at given value ranges², in addition to the portion of rental or ownership stock³ that may be available as suggested by recent movers over the past four years.
Estimates for municipalities are provided by the Census Bureau without the need for further analysis, municipalities are already included in Census Bureau datasets that contain places (though these do include Census Designated Places that are unincorporated). Conversely, we calculate estimates for unincorporated areas of counties by subtracting the estimates of municipalities from the county or counties that they lie within.
Data from the American Community Survey was collected from the period of 2017 to 2021 and may be considered as roughly from 2019 while data from the Comprehensive Housing Affordability Strategy⁴ was collected from 2015 through 2019 and may be considered as roughly from 2017. Income limits are provided by the U.S. Department of Housing and Urban Development in the form of Area Median Incomes for Federal Fiscal Year 2022⁵, and from the American Community Survey 2021 for the state median household income⁶.
The proposition allows for baselines to be calculated using the income limit of an adjacent jurisdiction. Adjacency is determined based on a county adjacency file from the National Bureau of Economic Research⁷. For these references, income limits are displayed for counties that may nor necessarily border municipalities yet do border the county or counties that the municipality lies within. This is done to provide more options for municipalities compared to determining adjacency based on coterminous borders which would be more restrictive.
Analysis and results
The home value, gross rent, and recent mover estimate data provided by HUD and the ACS is joined with income limit data to determine the portion of units that are affordable within each range for homes (for example, from $400,000 to $499,999) and rental units (for example, from $1,000 to $1,249) based on each income limit (for example, the area median income of the jurisdiction’s own county). The resulting dataset illustrates how the amount of housing that is considered as affordable within a jurisdiction differs based on the income limit that drives the affordability calculation.
Rental units are affordable if the gross rent of the unit is affordable at 60% of the selected income limit, while home ownership units are affordable if the value of the home is equal to or less than the income limit multiplied by 3.5 (to calculate the home value to income ratio). The home value to income ratio was derived from mortgages originated for home purchase in Colorado in 2019, made available through the Home Mortgage Disclosure Act Dataset published by the Consumer Finance Protection Bureau⁸.
The estimated baseline amount is further adjusted to consider the amount of housing that is not just affordable, but also available, by prorating the estimated amount of affordable housing by the portion of recent movers within that type of stock (owned or rented) for each jurisdiction. The end result of these aggregations gives localities a potential baseline and annual commitment estimates outlined by Proposition 123.
Note: Links to U.S. Census Bureau data are directed to a server that contains individual files for American Community Survey tables for the entire United States, these files are very large and require technical skill to analyze. To view this data more intuitively, we recommend visiting data.census.gov and searching for the relevant table (for example, Table B25063 regarding Gross Rents).