A 1987 study showed over 450 family names in common use in Beijing, but there were fewer than 300 family names in Fujian. Furthermore, a 2012 study found that there was the lowest amount of isonymy in surnames among the population around middle and lower reaches of Yangtze River both on the provincial and county levels. Additionally, it was found that counties with the highest values of isonymy were distributed in the provinces with high proportions of ethnic minorities. According to the dendrogram of surname distances, several clusters could be identified. Most provinces in a cluster were conterminous with one another. The one exception to this pattern could be explained by demic migration observed where the Han Chinese migrated to Northeastern China.