CREATE TABLE table_68973 ("Year" FLOAT, "Opponent" TEXT, "Competition" TEXT, "Score" TEXT, "Venue" TEXT, "Attendance" FLOAT)

How many years have less than 28,505 attendance?
SELECT AVG("Year") FROM table_68973 WHERE "Attendance" < '28,505'
SELECT AVG("Year") FROM "table_68973" WHERE "Attendance" < '28,505'