The number of Indians adopting US citizenship has decreased though they are the second biggest ethnic group to acquire the green cards.
According to the Annual Flow Report issued by Department of Homeland Security, the total number of people becoming naturalised US citizens was 6,60,477 in 2007.
The leading countries of origins of new citizens were Mexico with 122,258 followed by India at 46,871. Philippines, China and Vietnam took the third, fourth and fifth places respectively.
In 2005, the number of Indians who took citizenship was 35,962 or 6 per cent of the total; in 2006, the number rose to 47,542 or 6.8 per cent; and in 2007, it was 46,871 or 7.1 per cent.
The largest number of people naturalising lived in California followed by New York and Florida.
The DHS has pointed out that until the 1970s, majority of people naturalising were from European countries but with increased immigration from Asia, the arrival of Indo-Chinese refugees in the 1970s, and the historically higher naturalisation rate of Asian immigrants, the regional origin of new citizens shifted from Europe to Asia.
"Asia was the leading region of origin of new citizens in every year from 1976 to 2006, except 1996-2000 when IRCA legalisation immigrants, 90 per cent of whom were from North American countries, naturalised in large numbers.
"In 2007, however, the number of naturalisations of immigrants from North American countries slightly exceeded those of Asian immigrants, the report says.
Statistics show that North America and Asia were each the regions of origin of 36 per cent of people naturalising in 2007, followed by Europe with 13 per cent.