Hispanics account for about half the current growth rate of the US population, according to new figures released by the US Census Bureau.
Hispanic growth is down to births as well as immigration
Hispanics rose 3.6% to 41.3m in the year to July 2004. Overall, the US population went up 1% to 296m.
In 2003, Hispanics overtook blacks to become the largest US minority group.
The population growth for Asians ran a close second. The rises in both cases are attributed to higher birth rates and immigration.
In the 1990s, Hispanics accounted for 40% of the country's population increase. From 2000 to 2004, that figure grew to 49%.
US POPULATION GROUPS
Whites - 240m
Hispanics - 41.3m
Blacks - 39.2m
Asians - 14m
Native Americans - 4.4m
Native Islanders - 1m
(Totals do not equal population as people may belong to more than one group)
Source: US Census Bureau
But the Washington Post reports that in contrast to the 1990s, births in the US have now overtaken immigration as the largest source of Hispanic growth.
One academic specialising in US-Latin American relations saluted the boom.
"If we didn't have those elements, we would be moving into a situation like Japan and Europe, where the populations are greying in a way that is very alarming and endangering their productivity and endangering even their social security systems," Lewis W Goodman told the Associated Press news agency.
The Census Bureau classifies Hispanics as an ethnicity rather than a race, so Hispanics can be of any race.
This explains why the numbers for all races and ethnic groups do not match the total of almost 300m people who make up the US population as a whole.
The population of non-Hispanic whites indicating no other race increased just 0.3% in the past year to 197.8m.
Last year, the Census Bureau predicted that whites and minority groups overall would be roughly equal in size by 2050, with the Hispanic and Asian populations tripling by that time.