CREATE TABLE table_204_590 (id DECIMAL, "year" DECIMAL, "division" DECIMAL, "league" TEXT, "regular season" TEXT, "playoffs" TEXT, "open cup" TEXT, "avg. attendance" DECIMAL)

what was the difference in average attendance between 2010 and 2001 ?
SELECT ABS((SELECT "avg. attendance" FROM table_204_590 WHERE "year" = 2010) - (SELECT "avg. attendance" FROM table_204_590 WHERE "year" = 2001))
SELECT ABS((SELECT "avg. attendance" FROM "table_204_590" WHERE "year" = 2010) - (SELECT "avg. attendance" FROM "table_204_590" WHERE "year" = 2001))