CREATE TABLE table_58433 ("Season" TEXT, "Season premiere" TEXT, "Season finale" TEXT, "TV season" TEXT, "Ranking" TEXT, "Viewers  ( in millions ) " FLOAT)

What was the ranking of the season whose finale aired on May 15, 2011?
SELECT "Ranking" FROM table_58433 WHERE "Season finale" = 'may 15, 2011'
SELECT "Ranking" FROM "table_58433" WHERE "Season finale" = 'may 15, 2011'