Ethnic Kazakhs, a mix of Turkic and Mongol nomadic tribes who migrated into the region in the 13th century, were rarely united as a single nation. The area was conquered by Russia in the 18th century, and Kazakhstan became a Soviet Republic in 1936. During the 1950s and 1960s agricultural "Virgin Lands" program, Soviet citizens were encouraged to help cultivate Kazakhstan's northern pastures. This influx of immigrants (mostly Russians, but also some other deported nationalities) skewed the ethnic mixture and enabled non-ethnic Kazakhs to outnumber natives. Non-Muslim ethnic minorities departed Kazakhstan in large numbers from the mid-1990s through the mid-2000s and a national program has repatriated about a million ethnic Kazakhs thus far back to Kazakhstan. These trends have allowed Kazakhs to become the titular majority again. This dramatic demographic shift has also undermined the previous religious diversity and made the country more than 70 percent Muslim. Kazakhstan's economy is larger than those of all the other Central Asian states largely due to the country's vast natural resources. Current issues include: developing a cohesive national identity; managing Islamic revivalism; expanding the development of the country's vast energy resources and exporting them to world markets; diversifying the economy outside the oil, gas, and mining sectors; enhancing Kazakhstan's economic competitiveness; developing a multiparty parliament and advancing political and social reform; and strengthening relations with neighboring states and other foreign powers. - The World Factbook