At each wave, alcohol consumption was measured with a standard quantity–frequency index assessing beer, wine, and hard liquor consumption in the last 30 days. Respondents were asked how often they usually had each beverage in the last 30 days (using a 7-point scale ranging from 1 - ‘never’ to 7 – ‘every day’) and, when they had the beverage, on average how much they usually drank (using a 10-point scale ranging from 1 - ‘none’ to 10 -‘more than 8 drinks’). The quantity–frequency index, based on all three beverages, provides a measure of the average number of ounces of ethanol consumed per day in the last month (Armor and Polich, 1982). Consistent with prior research (Windle and Windle, 2012), a logarithmic transformation was applied to the index to improve normality.
