He Jun-dong et al. (2012) did a principal component analysis using the NRY haplogroup distribution frequencies of 45 populations, and the second principal component showed a close affinity between Kinh and Vietnamese who were most likely Kinh with populations from mainland southern China because of the high frequency of NRY haplogroup O-M88. The study said that Kinh often have NRY haplogroup O-M7 which is the characteristic Chinese haplogroup. Out of the study's sample of seventy-six Kinh NRY haplogroups, twenty-three haplogroups (30.26%) were O-M88 and eight haplogroups (10.53%) were O-M7. The study said that, in ancient northern Vietnam, it is suggested that there has been considerable assimilation of inhabitants from present-day southern China through immigration into the Kinh people.