Mapping the extent of unhealthy food advertising around schools in Tāmaki Makaurau/Auckland

Figures & data

Figure 1. Location and school roll (population) of primary and intermediate schools within the entire study area (A) and central Auckland (B). The category ‘Rural Area’ includes schools located in rural area, rural centres, minor urban, and secondary urban areas (Ministry of Education n.d.). Base Map: Statistics NZ (2017, 2021a).

Table

Key Concepts In the context of this study, children are defined as those attending primary education at one of Auckland’s primary (elementary school in the US) (‘full primary’: years 1–8; ‘contributing': years 1–6) or intermediate schools (middle school in the US) (years 7–8) (Ministry of Education 2022a). All 381 primary (full or contributing) and intermediate schools for which both Brien et al. (2023) and Huang et al. (2020) collected data were included in the present study. These are all classified as either state or state-integrated. The school food zone refers to the area around each school that is within 500 m walking distance of the school’s main entrance (Huang et al. 2020; Brien et al. 2023). This is the buffer zone size used most frequently in research on the presence of outdoor advertising around schools (Finlay et al. 2022). The type of food and drink advertising considered is limited to outdoor advertising on the fronts and premises of convenience stores, and on bus shelters. Unhealthy food and drink advertising is defined as those promoting products which are not recommended for marketing to children according to the WHO Regional Office for Europe Nutrient Profile Model (WHO 2015), in line with definitions applied by previous studies (Huang et al. 2020; Brien et al. 2023), however other previous NZ studies have used the terms ‘non-core’ and ‘core’ to define ‘unhealthy’ and ‘healthy’ foods. In the context of this study, the term ‘food/drink advertisement’ refers to advertisements of food items and/or non-alcoholic beverages. Exposure to unhealthy outdoor food/drink advertising is defined as the presence of a convenience store or bus stop displaying unhealthy food/drink marketing within the school food zone (Huang et al. 2020; Brien et al. 2023). Neighbourhood deprivation is multidimensional, comprising both social and material aspects; its level and experience vary across areas and population groups (Exeter et al. 2017). In NZ, deprivation at the school level was measured by school deciles until 2023. The Ministry of Education provided this measure for each school, based on the percentage of students living in an area of low socioeconomic status. The higher the decile of a school, the lower the proportion of students from a socioeconomically deprived area (Ministry of Education 2022b). School deciles for 2019 for the sampled schools are available from the school statistics of the New Zealand Ministry of Education (Ministry of Education 2022c). In January 2023, the newly introduced Equity Index (EQI) replaced the school decile as the preferred measure of socioeconomic disadvantage at school level (Ministry of Education 2023). Each school is assigned a numeric value between 344 and 569 points, based on 37 variables selected to measure the socio-economic circumstances of its student body (as measured in the previous three years). The higher the EQI, the more barriers to educational achievement the students of a school are expected to face (Ministry of Education n.d.). Given its relevance to policymakers, the EQI serves as the main indicator of deprivation in the present study. Alternatively, the NZ Index of Multiple Deprivation 2018 (IMD18) combines several domains of deprivation beyond education into an index which returns the level of deprivation at the neighbourhood level (Exeter et al. 2017). The IMD18 decile of each school’s neighbourhood was included as an alternative indicator for neighbourhood deprivation (Exeter et al. 2020).

Table 1. Overview of the original data sets.

Dataset; Publication	Study period (GSV image capture dates)	Data structure
Bus Stops; Huang et al. (2020)	August 2019 to February 2020 (February 2012 to May 2019)	573 schools; 512 bus stops; 842 advertisements
Convenience Stores - Primary Schools; Brien et al. (2023)	May 2020 to February 2021 (February 2012 to September 2020)	371 schools; 296 stores; 3693 advertisements
Convenience Stores - Intermediate and Additional Primary Schools; unpublished	September 2021 to March 2023 (February 2012 to January 2023)	62 schools; 114 stores; 1423 advertisements

Figure 2. Kernel density maps of the advertising score (A), school Equity Index (B), and Index of Multiple Deprivation (C) in central Auckland. Base Map: Statistics NZ (2017, 2021b).

Table 2. Regression coefficients and intercepts for linear regression of the advertising score with Equity Index and covariates.

	Model 1 (all)	Model 2 (all)	Model 3 (all)	Model 4 (Adv Score > 0)	Model 5 (Adv Score > 0)
Intercept	0.181 (0.099)	−0.04 (0.102)	−0.096 (0.078)	0.297 (0.086) ***	0.226 (0.094) *
EQI Score	0.0001 (0.0002)	0.0003 (0.0002)	0.00033 (0.00016) *	0.0003 (0.0002).	0.0004 (0.0002) *
Urbanity	–	0.192 (0.034) ***	0.086 (0.027) **	–	−0.042 (0.048)
Adv. Spaces	–	–	0.074 (0.004) ***	–	0.028 (0.004) ***
Adjusted R²	−0.002	0.073	0.465	0.0091	0.1619

Notes: Standard errors given in brackets. Statistical significance coded: < 0.001 ‘***’, < 0.01 ‘**’, < 0.05 ‘*’, < 0.1 ‘.’

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Data availability statement

The data reported in this study is available upon reasonable request.