The actual alcohol consumption behavior in individuals’ social contacts affects individuals’ alcohol consumption behavior. Figure 3 shows the smoothed bivariate relationship between the fraction of a principal's friends and family who drink heavily and abstain at one exam, and the average number of drinks per day at the following exam. Being surrounded by heavy drinkers increases by about 70% (95% CI: 35% to 142%) the amount of alcohol a person drinks at the next exam compared to those who are not connected to any heavy drinkers. Conversely, being surrounded by abstainers cuts in half the amount of alcohol a person drinks at the next exam.
