Water Vending Machine Methodology

To understand demand for water vending machines in San Diego County, Voice of San Diego analyzed data from the California Department of Public Health, the agency responsible for licensing and inspecting the machines.

We started with a spreadsheet provided by the department, which lists the street addresses of every water vending machine licensed in 2023. We standardized these addresses and then converted each address to a latitude and longitude point using a geocoding service. Not every machine was matched to its exact location because of occasional typos in the original addresses.

Merging the water vending machine location data with a map of Census tracts in San Diego allowed us to count the approximate number of water vending machines in each tract. We then calculated the following fields, using 2022 American Community Survey 5-year estimates:

• The number of vending machines per 10,000 people in a Census tract. 
• The percentage of people 25 years and over with no college education. (That is, people with at most a GED or a high school degree.) 
• The percentage of the population that is non-white Hispanic or Latino. 
• The percentage of housing units that are renter-occupied. 
• The percentage of the population below the poverty line.
• The percentage of the population that is not a U.S. citizen.

We ranked the Census tracts by each of the factors above, comparing the ratio of vending machines to people in the bottom and top fifth of each category. For example, we compared the number of water vending machines per person in the top 20% of Census tracts for renter-occupied housing to the ratio of machines to people in the tracts in the bottom 20% for renter-occupied housing.