The number of Hispanics has grown by more than one-third since 1980 and now represents 8.1 percent of the nation's population, the Census Bureau says. In a report issued Tuesday, the bureau also said the rate of Hispanic growth is nearly five times that for the rest of the population, and more than half of all Hispanics in this country live in just two states: California and Texas. The bureau estimated there were 19.4 million Americans of Hispanic background as of last March. The nation's non-Hispanic population increased by about 7 percent in the same period.