There isn't more hispanics under 18 than whites under 18. You're reading that graph wrong. The graph simply shows that 33 percent of the Hispanic population is under 18 vs 19 percent of whites. The white population is 200 million while the Hispanic population is 55 million. Furthermore, Hispanic is simply a cultural definition, like Slavic. Ted Williams was half Mexican. Was he "white?" Or is a multi generational Hispanic American who doesn't speak a lick of Spanish more "white" than Manu Ginobili? As you can see defining people this way is rather arbitrary.