Ethnic Kazakhs, a mix of Turkic and Mongol nomadic tribes with additional Persian cultural influences, migrated to the region in the 15th century. The area was conquered by Russia in the 18th and 19th centuries, and Kazakhstan became a Soviet Republic in 1925. Repression and starvation associated with forced agricultural collectivization led to a massive number of deaths in the 1930s. During the 1950s and 1960s, the agricultural "Virgin Lands" program led to an influx of settlers (mostly ethnic Russians, but also other nationalities) and at the time of Kazakhstan’s independence in 1991, ethnic Kazakhs were a minority. 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 (from Uzbekistan, Tajikistan, Mongolia, and the Xinjiang region of China) back to Kazakhstan. As a result of this shift, the ethnic Kazakh share of the population now exceeds two-thirds. Kazakhstan's economy is the largest in the Central Asian states, mainly due to the country's vast natural resources. Current issues include: diversifying the economy, obtaining membership in global and regional international economic institutions, enhancing Kazakhstan's economic competitiveness, and strengthening relations with neighboring states and foreign powers.