CREATE TABLE table_8577 ("Year" FLOAT, "Competition" TEXT, "Venue" TEXT, "Position" TEXT, "Notes" TEXT)

what is the year when the notes is 5000 m and the competition is world junior championships in athletics?
SELECT COUNT("Year") FROM table_8577 WHERE "Notes" = '5000 m' AND "Competition" = 'world junior championships in athletics'
SELECT COUNT("Year") FROM "table_8577" WHERE "Competition" = 'world junior championships in athletics' AND "Notes" = '5000 m'