GIS Research Project

GIS for Population Science Research Project

Blog Post 1

In December 2014, Minneapolis, Minnesota passed a city ordinance allowing for the construction of accessory dwelling units (ADUs, also known as “granny flats”) on existing single-family lots. The ordinance was the first in a series of steps to address the costs of housing in the city by increasing housing supply. In 2018, Minneapolis continued this approach by banning single-family zoning, thus requiring a 3-unit minimum on each lot for new construction.

The 2014 ordinance allows single-family homeowners to construct ADUs on their property. Theoretically, this should add housing supply to the city and apply downward pressure on housing costs. Critics argued ADUs wouldn’t make a significant impact on housing supply since they are relatively expensive to build (around $100,000 each at the time) and the property owner had to continue to reside in either the existing home or the ADU. In other words, they would primarily be used by family members and would not enter the general rental market.

The 2018 ordinance banning single-family zoning was one of the first of its kind. Single-family zoning is highly valued by homeowners but advocates of high-density housing argue it should be phased out. It is highly unusual for existing single-family zoning to be modified, so Minneapolis is entering uncharted territory for housing policy.

This research project will analyze changes in rental affordability in Minneapolis between 2014, when the ADU ordinance was passed, and 2020. Comparing housing costs before and after the ADU ordinance and single-family zoning ban will provide evidence of the effects of these changes in housing policy. The research question is how did rental affordability change in Minneapolis, Minnesota, five years after the city passed an ordinance allowing ADUs on single family lots in December 2014 and two years after the city banned single family zoning in 2018?

I will map 3 variables from the U.S. Census Bureau American Community Survey Public Use Microdata (2014 and 2020) related to housing costs in Minneapolis, Minnesota, in 2014 and 2020, by census tract. The variables are percent of renters in each tract (derived from the TEN variable, housing tenure), the percent of renters who are cost burdened (derived from GRPIP, gross rental as a percentate of household income), and the change in percent of renters who are cost burdened from 2014 to 2020. “Cost burdened” is defined as paying greater than 30% of income towards housing costs.

I will produce the following maps and tables:

• Map 1: Percent of all residents who are renters in each census tract in 2014.
• Map 2: Precent of all residents who are renters in each census tract in 2020.
• Map 3: Percent of renters in each census tract who are cost burdened in 2014.
• Map 4: Percent of renters in each census tract who are cost burdened in 2020.
• Map 5: Change in percent of renters who are cost burdened from 2014 to 2019.
• Table 1: List of census tracts with percent cost burdened in 2014, in 2020, and change in percentage over the 5-year period.