what is the average total hospital cost if there is disloc acromioclavic-cl since 2105?
select avg(t1.c1) from ( select sum(cost.cost) as c1 from cost where cost.hadm_id in ( select diagnoses_icd.hadm_id from diagnoses_icd where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'disloc acromioclavic-cl' ) ) and strftime('%y',cost.chargetime) >= '2105' group by cost.hadm_id ) as t1