Both asthma and obesity are becoming increasingly common in the United States. The latest research to examine relationships between the conditions finds that obesity is a risk factor for repeated hospital visits in children with asthma. In the U.S., the percentage of children with obesity "has more than tripled since the 1970s." Between 2011 and 2014, around 17 percent of children and adolescents aged 2–19 were obese. Asthma is also becoming more common. In 2001, around 1 in 14 adults had asthma — but by 2009, that number had increased to 1 in 12. This means that in the U.S., around 25 million people have asthma. This sharp rise applies to children, too; in 2009, around 1 in 10 children had asthma. The biggest increase was measured in black children, who experienced an almost 50 percent increase from 2001 to 2009.