Horses with mild EIPH earn more prize money than those with more severe EIPH.[12] While single bouts of EIPH may not even be apparent to the rider, owner or trainer of a horse unless an endoscopic examination is undertaken, the effect on performance within a single race appears to be significant but relatively subtle.[13] In a 2005 study, horses finishing races with grade 4 EIPH were on average 6 metres behind those finishing with grade 0.[13] However, the effect of repeated bouts of EIPH that occur with daily training may lead to more significant changes and a greater degree of tissue damage over time[3] with consequent loss of lung function.