One large scale study on a group of young adults in New Zealand showed 95.6% had at least 1 wisdom tooth with an eruption rate of 15% in the maxilla and 20% in the mandible.[30] Another study on 5000 army recruits found 10,767 impacted wisdom teeth.[31]:246 The frequency of impacted lower third molars was found to be 72% in a Swedish study,[3] and the frequency of retained impacted wisdom teeth that are free of disease and symptoms is estimated to be between 11.6% to 29%, a percentage which drops with age.[30]