*This paper investigates a new mechanism explaining how cultural differences represent a barrier to migration. I provide evidence that cultural distance between the origin and destination country negatively affects migrants' earnings. By increasing the human capital investment necessary for cultural adaptation, it increases the time needed to reach a given level of income. Using a triple difference estimator, I show that cultural distance represents an opportunity cost reducing migrants' earnings. Finally. I show that my results cannot be explain neither by composition effects or by selective out migration.

**The objective of this study is to analyze the determinants of Preferential Trade Agreements Networks dynamics. We propose a theoretical framework based in an extension of Baldwin (1995) to rationalize the determinants of PTA formation as a way to maximize preferential market access and/or diminish market discrimination. To build the empirical model we use called Stochastic Actor Oriented Models (SAOM) proposed by Snijders (2001). Specifically, we use three sets of variables to model countries' motivation to change their PTA neighborhood at each moment. The first is related to trade cost and. The second group of variables is related to political economy effects. And finally we include a variable related to trade specialization, which has not been used in earlier works to explain PTAs. Following Snijders et al. (2012) we also control for hierarchy structures of the PTA, and we extend their work by analyzing the change in this phenomenon when considering a broader period of time. Results show that the signs of usual variables behave as expected in the literature for the first period but hierarchy effect dilutes after 2004. As a contribution to existing literature we found that trade rivalry between countries is also significant in explaining the dynamics of PTA.