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