In the United States, gout is twice as likely to occur in African American males as it is in European Americans. Rates are high among the peoples of the Pacific Islands and the Māori of New Zealand, but rare in Australian aborigines, despite a higher average concentration of serum uric acid in the aboriginal group. Gout has become common in China, Polynesia, and urban sub-Saharan Africa. Some studies have found that gout attacks occur more frequently in the spring. This has been attributed to seasonal changes in diet, alcohol consumption, physical activity, and temperature.