Migration has long played a key role in shaping the size and distribution of the population of Pakistan. Since the partition of the British Indian Empire in 1947, and up to recent and ongoing conflicts within the region, Pakistan has been the destination for large numbers of cross-border migrants and refugees. These migrant groups, together with the growing number of rural people displaced by agricultural modernization and mechanization, have contributed to the substantial increase in the levels of urbanization in Pakistan, especially in the more industrialized provinces of Punjab and Sindh. At the same time, like the people of so many low- and middle-income nations, Pakistani citizens have sought work abroad, and in the 1970s large scale labor migration to the Middle East began in earnest. Remittances have since become an important component of the national economy and of the livelihoods of many households.