Question: Compare the graduate cohort for Auburn University from 2011 to 2013?
SQL: SELECT SUM(CASE WHEN T2.year = 2011 THEN T2.grad_cohort ELSE 0 END), SUM(CASE WHEN T2.year = 2012 THEN T2.grad_cohort ELSE 0 END), SUM(CASE WHEN T2.year = 2013 THEN T2.grad_cohort ELSE 0 END) FROM institution_details AS T1 INNER JOIN institution_grads AS T2 ON T1.unitid = T2.unitid WHERE T2.gender = 'B' AND T2.race = 'X' AND T1.chronname = 'Auburn University'