Colombia is the third-most populous country in Latin America, after Brazil and Mexico. Migration from rural to urban areas has been prevalent. The urban population increased from 57% of the total population in 1951 to approximately 74% by 1994. Thirty cities have a population of 100,000 or more. The nine eastern lowlands departments, constituting about 54% of Colombia's area, have less than 3% of the population and a density of less than one person per square kilometer (two persons per sq. mi.). Ethnic diversity in Colombia is a result of the intermingling of indigenous peoples, Spanish colonists, and Africans. Today, only about 1% of the people can be identified as fully indigenous on the basis of language and customs.