CREATE TABLE table_21881 ("Season" TEXT, "Date" TEXT, "Driver" TEXT, "Team" TEXT, "Chassis" TEXT, "Engine" TEXT, "Laps" TEXT, "Miles  ( km ) " TEXT, "Race Time" TEXT, "Average Speed  ( mph ) " TEXT, "Report" TEXT)

When 2005 is the season how many drivers are there?
SELECT COUNT("Driver") FROM table_21881 WHERE "Season" = '2005'
SELECT COUNT("Driver") FROM "table_21881" WHERE "Season" = '2005'