They have a long standing, shared cultural history and value system that is ingrained into the every day lives of the society.

Like it or not, the overwhelming majority of human history and culture is ethnocentric. It should not be a surprise that the ethnic values, ethics, and ways of living continue to be the dominant force in an area that has remained the same demographically for centuries.

That's not to say the culture, values, and ethics are inextricably bound to the ethnicity, but it is without a doubt a vehicle for sustainment and major factor in policy success or failure.