CREATE TABLE "historical_data" (
  "rank" text,
  "province" text,
  "population_2011" real,
  "percentage" real,
  "population_estimate_2013" real
);

Question: What is the lowest 2013 population estimate of south africa, which has a percentage greater than 19.8 and a 2011 population greater than 51,770,561?
SQL: SELECT MIN("population_estimate_2013") FROM "historical_data" WHERE "percentage">19.8 AND "province"='south africa' AND "population_2011">'51,770,561';

Question: What is the rank of the gauteng province?
SQL: SELECT "rank" FROM "historical_data" WHERE "province"='gauteng';

Question: What is the lowest 2013 population estimate of the province with a 23.7 percentage?
SQL: SELECT MIN("population_estimate_2013") FROM "historical_data" WHERE "percentage"=23.7;