DOI: 10.5061/dryad.hhmgqnkkq
title: Changes in sugar-sweetened beverage consumption in the first two years (2018 – 2020) of San Francisco’s tax: A prospective longitudinal study

description: Background: Sugar-sweetened beverage (SSB) taxes are a promising strategy
 to decrease SSB consumption, and their inequitable health impacts, while
 raising revenue to meet social objectives. In 2016, San Francisco passed a
 one cent per ounce tax on SSBs. This study compared SSB consumption in San
 Francisco to that in San José, before and after tax implementation in
 2018. Methods & findings: A longitudinal panel of adults (n =
 1,443) was surveyed from zip codes in San Francisco and San José, CA with
 higher densities of Black and Latino residents, racial/ethnic groups with
 higher SSB consumption in California. SSB consumption was measured at
 baseline (11/17–1/18), one (11/18–1/19), and two years (11/19-1/20) after
 the SSB tax was implemented in January 2018. Average daily SSB consumption
 (in ounces) was ascertained using the BevQ-15 instrument and modeled as
 both continuous and binary (high consumption: ≥6 oz (178 ml) versus low
 consumption: &lt;6 oz) daily beverage intake measures. Weighted
 generalized linear models (GLMs) estimated difference-in-differences of
 SSB consumption between cities by including variables for year, city, and
 their interaction, adjusting for demographics and sampling source. In San
 Francisco, average SSB consumption in the sample declined by 34.1% (-3.68
 oz, p = 0.004) from baseline to 2 years post-tax, versus San José which
 declined 16.5% by 2 years post-tax (-1.29 oz, p = 0.157), a
 non-significant difference-in-differences (-17.6%, adjusted AMR = 0.79, p
 = 0.224). The probability of high SSB intake in San Francisco declined
 significantly more than in San José from baseline to 2-years post-tax
 (AOR[interaction] = 0.49, p = 0.031). The difference-in-differences of
 odds of high consumption, examining the interaction between cities, time
 and poverty, was far greater (AOR[city*year 2*federal poverty level] =
 0.12, p = 0.010) among those living below 200% of the federal poverty
 level 2-years post-tax. Conclusions: Average SSB intake declined
 significantly in San Francisco post-tax, but the difference in differences
 between cities over time did not vary significantly. Likelihood of high
 SSB intake declined significantly more in San Francisco by year 2 and more
 so among low-income respondents.
description: The three waves of the study utilized
 a “push-to-web” data collection method, in which sampled households were
 sent an invitation via mail, text, and/or E-mail to complete an online Web
 questionnaire. Additional web completes were collected using a
 non-probability web panel. Questionnaires were completed in English,
 Spanish, or Chinese. Data from each wave were appended together--each
 row/observation is unique to participant ID and wave. Variables for the
 study were constructed using Stata. More details on methodology can be
 found in SSB_Sampling_and_Data_Collection_Methodology.pdf and
 SSB_Analytic_Sample_Creation_Flowchart.pdf.
description: Data are in CSV format. Documentation is in PDF format. Code is
 in Stata format (.do) and can also be opened as a text file.