Any member of a people originating in northern India but now living worldwide, principally in Europe. Most speak Romany in addition to the local language. It is thought that Roma groups left India in successive migrations, reaching western Europe by the 15th century. In the 20th century they spread to North and South America and Australia. Because of their often nomadic and marginalized lives, population figures are largely guesswork; estimates in the early 21st century range from two to three million. They have often been persecuted and harassed; the Nazis killed about 400,000 Roma in extermination camps. How many Roma retain a nomadic lifestyle is unclear, but those that migrate do so at least seasonally along patterned routes that ignore national boundaries. They pursue occupations compatible with a nomadic life. In the past they were often livestock traders, tinkers, fortune-tellers, and entertainers; today they are often car mechanics, auto-body repairmen, and workers in traveling circuses and amusement parks. Confederations of 10–100 families elect chieftains for life, but their title is not heritable. Women are organized as a group within the confederation and represented by a senior woman. Modern Roma culture faces erosion from urban influences; integrated housing, economic independence, and intermarriage with non-Roma have weakened Roma law.