CREATE TABLE table_203_592 (id DECIMAL, "institution" TEXT, "location" TEXT, "athletic nickname" TEXT, "undergraduate enrollment" DECIMAL, "graduate enrollment" DECIMAL, "total enrollment" DECIMAL, "2013 endowment\ ( and us rank ) " TEXT, "academic staff" DECIMAL, "motto" TEXT)

colombia has the highest graduate enrollment at 15,760 . what school has the next highest ?
SELECT "institution" FROM table_203_592 WHERE "graduate enrollment" < (SELECT "graduate enrollment" FROM table_203_592 WHERE "institution" = 'columbia university') ORDER BY "graduate enrollment" DESC LIMIT 1
SELECT "institution" FROM "table_203_592" WHERE "graduate enrollment" < (SELECT "graduate enrollment" FROM "table_203_592" WHERE "institution" = 'columbia university') ORDER BY "graduate enrollment" DESC NULLS LAST LIMIT 1