The data on self-reported hearing loss was collected using a standard questionnaire with questions
adopted from the 1977 National Health Interview Survey (Ries, 1982). The first part of the
questionnaire looked at hearing difficulties include whether subjects were total deaf or had any
other hearing trouble. The second focused on traffic policemen with any type of difficulty. This
includes a self-rating scale with subjects classify their hearing in each ear as good, a little trouble
hearing, lot of trouble of hearing, or deaf. Policemen who reported any type of difficulty hearing
on the screening questions and any difficulty hearing on the self-rating scale in one or both ears
were classified as having self-reported hearing loss.