Fig. 1.

An example of tipping based on the framework used in Andreoni et al. (3). In $t=1$, everyone faces material incentives that favor coordinating on blue over coordinating on green (Left column). The distribution of indifference points is relatively unfavorable for green as a result (Center column), and everyone chooses blue (Right column). As time passes, individuals experience changing material incentives. The distribution of thresholds drifts steadily downward, in favor of green, but for a while (e.g., $t\le 5$) this generates little change in behavior. At some point (e.g., $t\ge 6$), behavior change accelerates, and the population transitions rapidly to a new norm. Broadly speaking, Andreoni et al. (3) examine when the rapid change in behavior does or does not follow the change in incentives.