Why the prevalence and incidence of hearing loss for all industries combined did not change much during 1981-2010 (about 1-2%), but the adjusted risk decreased significantly (46%)?

Why the prevalence and incidence of hearing loss for all industries combined did not change much during 1981-2010 (about 1-2%), but the adjusted risk decreased significantly (46%)?

 

  1. 15 points) Why the prevalence and incidence of hearing loss for all industries combined did not change much during 1981-2010 (about 1-2%), but the adjusted risk decreased significantly (46%)?
  2. (15 points) Why the prevalence for hearing loss among workers in Healthcare and Social Assistance were increasing, and what factors may have contributed to?