According with WAO (World Allergy Organization), perennial rhinitis predominates in South America, Asia, Africa and Australia; perennial and seasonal rhinitis occur commonly in the U.S.A. and Japan. Seasonal rhinitis predominates in Europe. In one study in London of adults between the ages of 16 and 65 years, in 1991 the prevalence of rhinitis was 16%; of these, 8% had perennial symptoms, 6% perennial and seasonal symptoms, and 2% seasonal symptoms alone. As with asthma, both seasonal and perennial rhinitis seem to be increasing. The 2004-05 National Health Survey stated that 3.2 million Australians (approximately 16.1% of the population) self-reported experiencing symptoms of hay-fever and perennial rhinitis. The prevalence was found to be highest amongst those aged 25-34 and was slightly higher among females (1.7 million) than males (1.5 million).