The organizations are highly varied, and all of them have to be authorized by the relevant supervisory agencies, as indicated in the preceding sections. Over the last 15 years, the network has grown at a rate of 4% per year, which has involved significant improvements, including the construction of expressways and the four-lane expansion of the main highways leading to the border crossings. The others contract firms such as Agrotropic and Productos de Peten. There are over 30 shipping companies that provide maritime transport services to the leading ports around the world.