Distribution of participant choices.

<p>The radii of the circles are calculated based on the percentage of participants choosing a particular effort level over the total number of participants per country-treatment. The total number of participants per country-treatment is available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187840#pone.0187840.t001" target="_blank">Table 1</a>.