what is the yearly average amount of cerebral drain r ventricular drain that patient 83038 had since 07/27/2105?
select avg(outputevents.value) from outputevents where outputevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 83038 ) ) and outputevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'cerebral drain r ventricular drain' and d_items.linksto = 'outputevents' ) and strftime('%y-%m-%d',outputevents.charttime) >= '2105-07-27' group by strftime('%y',outputevents.charttime)