WASHINGTON: Asians and Hispanics are the fastest-growing ethnic groups in the US albeit for very different reasons according to the US Census Bureau.

New data from the government body show that the Hispanic population of the country stood at 54m in July 2013, up 2.1% on the previous year, while the Asian population totalled 19.4m, a growth rate of 2.9%.

But while the increase in the Hispanic population was driven primarily by natural increase (births minus deaths), that of Asians was due more to international migration. For Hispanics, the relative proportion was 78:22, for Asians, 39:61.

This could be seen to some extent in the differing age profiles for these groups. The median age of Asians was 36.3 while that of the Hispanic population was some eight years younger, at 28.1.

Among the other groups identified in the census are Native Hawaiians and Other Pacific Islanders (up 2.3% to 1.4m), American Indians and Alaska Natives (up 1.5% to 6.4m) and blacks or African-Americans (up 1.2% to 45m).

The non-Hispanic white population grew marginally, up 0.1% to 197.8m, and only then thanks to migration – this was the only group to record a natural decrease. This group's share of the total population now stands at 63.0%.

Asians and Hispanics are skewed to the west of the country, reflecting the geographical practicalities of migration. New Mexico has the highest percentage of Hispanics (47.3%) while California has the largest population (14.7m); Texas, however, had seen the largest increase, with a 213,000 rise in numbers since July 2012.

Asians were a majority in Hawaii (56%) and most numerous in California (6.1m), which also registered the largest numeric increase – 142,000 – between 2012 and 2013.

But the state showing the fastest growth in numbers of both Asians and Hispanics was North Dakota, where fracking is fuelling an economic boom as more than 1m barrels of oil are produced every day. The number of Hispanics jumped 17%, that of Asians 8.4%, although total number remained relatively small.

Data sourced from US Census Bureau, Time; additional content by Warc staff