How common are denials for third-class airman medical certificates?

Response by the Federal Air Surgeon
Over the past 3 years, the number of denials of third-class airman medical certificates has ranged from approximately 2000 to 2500 per year based on approximately 135,000 to 140,000 applications for third-class airman medical certification per year. Most of these denials resulted because of a failure of the applicants to provide sufficient information for the FAA to make a favorable decision.