Seroprevalence of H . pylori infection in asymptomatic subjects without a history of H . pylori eradication in birth cohort against age. Each line connects the values for the same cohort-group in different age group. For example, the first line shows the seroprevalence of H. pylori in a birth cohort of 1972–77 for ages of 22–39 years, and the second line shows the seroprevalence of H. pylori in a birth cohort of 1966–71 for ages of 28–45 years. All younger birth cohorts at the same age have a lower seroprevalence of H. pylori than older birth cohorts.