How many more people, in terms of percentage, belonged to the biggest age group compared to the 2nd and 3rd biggest age groups combined?
return age  groups ;return percentages of people of  #1 ;return the  highest of #2 ;return the  2nd highest of #2 ;return the  3rd highest of #2 ;return sum of #4 and  #5 ;return the  difference of #3 and  #6
['select', 'project', 'aggregate', 'aggregate', 'aggregate', 'arithmetic', 'arithmetic']