The number of people sharing a single given name or surname depends on the frequency of the name and size of the population. The United States Census Bureau calculates the number of people who share each name by examining census questionnaires and extrapolating the data.
Using statistical techniques, the U.S. Census Bureau calculates that the U.S. population includes 2.4 million people with the surname Smith, 1.9 million named Johnson, 1.5 million named Williams, 1.4 million named Brown and 1.4 million named Jones. The same data set shows that 3.3 percent of males are named James, and 3.2 percent are named John. Similarly, 2.6 percent of females share the name Mary, and 1 percent are named Patricia.