The primary hormone produced by the male testes is testosterone, a steroid hormone important in the development of the male reproductive system, the maturation of sperm cells, and the development of male secondary sex characteristics such as a deepened voice, body hair, and increased muscle mass.
Foreign investments in the US average $2.4 trillion, while American investments in other countries total $3.3 trillion. Consumer spending comprised 71% of the US economy in 2013, and the United States has the largest consumer market in the world. As a result, the US possesses not only the largest economy, but also one of the most stable in the world. Economic History. The United States has had the world's largest national economyânot including the benefit of colonial empiresâsince the 1890s.
United States Economy. The United States of America has the world's largest national economy. It makes up roughly 17 to 22 percent of the world's gross domestic product (GDP). The currency of the United States, the dollar, is the most widely used currency in international trade, as well as the world's foremost reserve currency.