**Objective:** According to the prediction of [Tamas David-Barrett’s (2019) model](https://www.nature.com/articles/s41598-019-39025-4), to protect your child from free-riders, you need to provide as many siblings as possible. His theoretical study showed that falling fertility changes the structure of social networks which weakens the mechanism for eliminating free-riders and could lead to a less cooperative society. Urbanization, increasing population, and migration decrease the number of interacting relatives and could cause the same effect. The recent demographic transition enhances the importance of this topic. We aimed to test his hypothesis using worldwide data. **Methods:** We searched the Web of Knowledge to extract all the studies that conducted a dictator game and collected the results of the games to create an index that measures cooperativity. We also collect the fertility rate of the place from the time when the subjects were born, and data of urbanization and migration. We study the relationship between cooperativity and demographic variables. **Results:** Our study is still ongoing. **Conclusion:** If David-Barrett’s hypothesis is right, demographic transition has a significant effect on alienation, our trust in each other, and how we solve large-scale cooperation problems. In case the effect operates differently the model needs to be revised. Either of the results helps us to understand how demographic transition affects our society, everyday life and human relationships. This project is part of the [*Structural Microfoundations theory of the society* project](https://www.microfoundations.world/), established by [Tamas David-Barrett](https://www.tamasdavidbarrett.com/).