We measured affiliation with six different peer crowds (Hipster, Country, Hip Hop, Partier, Homebody and Young Professional; figure 1). These informal names are used only for reporting purposes, and the names did not appear on the survey; instead of using names or labels, affiliation with the peer crowd was based on photo selection. Based on formative research,14 (link) we used the ‘I-Base Survey’ measure to determine peer crowd affiliation. Participants viewed a grid of images of young adults that had been consistently selected to represent the various peer crowds in focus groups. Survey respondents were instructed to choose three photos each from a male and female grid that ‘best fit into your main group of friends’; the peer crowd that was represented by each photo then scored 3, 2 or 1 point based on rank. Participants were also asked the same question for those who ‘least fit into your main group of friends’, scoring −1, −2 and −3, respectively. Scores from the male and female grid selections were added together, so the total score for each peer crowd ranged from −12 to 12. For example, if an individual chose all ‘Hipster’ pictures (three male and three female) as the pictures that best fit their friend group, and no Hipster pictures were selected as ‘least likely to fit’, they would receive a score of (3+2+1 (male picture selection) + 3+2+1 (female picture selection) = 12 total on the continuous Hipster score variable. Scores for affiliation with each peer crowd were analysed as continuous variables. In addition, a single categorical variable reflecting the ‘best fit’ peer crowd affiliation was created based on the peer crowd with the highest score. For example, if a person selected Hipster and partier images and scored 8 points based on Hipster selection and 4 points based on Partier picture selection, they would be classified as Hipsters in the categorical variable.