What is the lowest 2013 population estimate of the province with a 23.7 percentage?
CREATE TABLE "historical_data" (
  "rank" text,
  "province" text,
  "population_2011" real,
  "percentage" real,
  "population_estimate_2013" real
);
SELECT MIN("population_estimate_2013") FROM "historical_data" WHERE "percentage"=23.7;