What was the population of Green County?
CREATE TABLE "wisconsin_counties_ranked_by_per_capita_" (
  "county" text,
  "per_capita_income" text,
  "median_household_income" text,
  "median_family_income" text,
  "population" real,
  "number_of_households" real
);
SELECT MIN("population") FROM "wisconsin_counties_ranked_by_per_capita_" WHERE "county"='green';