Humans are social beings, and acts of prosocial behavior may be influenced by social comparisons. To study the development of prosociality and the impact of social comparisons on sharing, we conducted experiments with nearly 2500 children aged 3-12 years across 12 countries across five continents. Children participated in a dictator game where they had the opportunity to share up to 10 of their stickers with another anonymous child. Then, children were randomized to one of two treatments. In the "shared a little" treatment children were told that another child from their school had shared 1 sticker, whereas in the "shared a lot" treatment children were told that another child from their school had shared 6 stickers in the same game. There was a strong increase in baseline sharing with age in all countries and in both treatments. The "shared a lot" treatment had a positive treatment effect in increasing sharing overall, which varied across countries. However, cross-cultural comparisons did not yield expected significant differences between collectivist and individualist countries. Our results provide interesting evidence for the development of sharing behavior by age across the world and show that social information about the sharing of peers is important for children's decision making.