How many more people, in terms of percentage, belonged to the most common ancestry compared to the three least common ancestries combined?
return ancestries ;return percentages of people of  #1 ;return the  highest of #2 ;return the  three lowest of #2 ;return sum of #4 ;return the  difference of #3 and  #5
['select', 'project', 'aggregate', 'aggregate', 'aggregate', 'arithmetic']