CREATE TABLE table_name_91 (income_inequality_1994_2011__latest_available_ VARCHAR(255), population_2011 VARCHAR(255))
What is the latest available income inequality for the country with a population of 21,315,135?
    
SQL: SELECT income_inequality_1994_2011__latest_available_ FROM table_name_91 WHERE population_2011 = "21,315,135"