Because some economies are stronger than others, and some countries don't use the dollar
I thought it was history but it's lil ol math.
Explanation:
Columbus lands in South America
Explorer Christopher Columbus sets foot on the American mainland for the first time, at the Paria Peninsula in present-day Venezuela. Thinking it an island, he christened it Isla Santa and claimed it for Spain.
Columbus was born in Genoa, Italy, in 1451. Little is known of his early life, but he worked as a seaman and then a sailing entrepreneur. He became obsessed with the possibility of pioneering a western sea route to Cathay (China), India, and the fabled gold and spice islands of Asia. At the time, Europeans knew no direct sea route to southern Asia, and the route via Egypt and the Red Sea was closed to Europeans by the Ottoman Empire, as were many land routes. Contrary to popular legend, educated Europeans of Columbus’ day did believe that the world was round, as argued by St. Isidore in the seventh century. However, Columbus, and most others, underestimated the world’s size, calculating that East Asia must lie approximately where North America sits on the globe (they did not yet know that the Pacific Ocean existed).
