Two of the main shocks that affect international trade are price and tariff changes. The present thesis covers these two topics. The first chapter shows that the transmission of international agricultural prices to local producers is asymmetric, with downward price movements being transmitted more strongly than upward price movements. This seems to be due to the market power that intermediaries have on these markets. The second chapter looks at the way Peruvian firms are affected by market access conditions and it shows that it isn't only the direct tariff that firms face that plays a role but also the tariff he faces relative to the tariff that competitors from other countries face. The last chapter shows that the effect of these relative tariffs depends on the distance to the destination country, with the effect being stronger when exporting to closer countries.