Although it is true that Hans are the majority in all major regions of China, still there are significant ethnic concentrations in regions, e.g. see ethnic auto

Although it is true that Hans are the majority in all major regions of China, still there are significant ethnic concentrations in regions, e.g. see ethnic autonomous areas listed here (http://en.wikipedia.org/wiki/Autonomous_entities_of_China http://en.wikipedia.org/wiki/Autonomous_entities_of_China) other than Tibet and Xinjiang. History shows that large empires with regions of diversity can catastrophically divide up after long periods of being a single entity.