Politically, the Marshall Islands is a presidential republic in free association with the United States, with the US providing defense, subsidies, and access to U.S. based agencies such as the FCC and the USPS. With few natural resources, the islands' wealth is based on a service economy, as well as some fishing and agriculture; aid from the United States represents a large percentage of the islands' gross domestic product. The country uses the United States dollar as its currency.