When was the last year when Katharine Hepburn won?
CREATE TABLE "list_of_superlative_academy_award_winner" (
  "superlative" text,
  "actress" text,
  "record_set" text,
  "year" real,
  "notes" text
);
SELECT MAX("year") FROM "list_of_superlative_academy_award_winner" WHERE "actress"='katharine hepburn';