The unfenced, rural mountainous and desert border between Arizona and Mexico has become a major entrance area for unlawful migration to the United States, due in part to the increased difficulty of crossing illegally into California. Each year there are several hundred migrant deaths along the Mexico-U.S. border.[20] Often, migrants employ people smugglers (known as "coyotes") who promise a safe passage into the United States and are paid up to 3 to 6 thousand[21] for passages that include long walking distances or 7 to 14 thousand[clarification needed] for an easier travel per person they assist in crossing the border.[22] The difficulty and expense of the journey has prompted many migrant workers to stay in the United States longer or indefinitely.[23]