Piracy is robbery committed at sea, or sometimes on the shore, by an agent without a commission from a sovereign nation. One who commits piracy by engaging in robbery, pillaging, or plundering at sea is known as a pirate. Seaborne piracy against transport vessels remains a significant issue (with estimated worldwide losses of US$13 to $16 billion per year), particularly in the waters between the Pacific and Indian Oceans, off the Somali coast, and in the Strait of Malacca and Singapore, which are used by over 50,000 commercial ships a year. A recent surge in piracy off the Somali coast spurred a multi-national effort led by the United States to patrol the waters near the Horn of Africa to combat piracy. While boats off the coasts of South America and the Mediterranean Sea are still assailed by pirates, the advent of the United States Coast Guard has nearly eradicated piracy in U.S. waters and the Caribbean Sea. The Jolly Roger is the traditional flag of European and American pirates.