Between 1918 and 1920, how many more millions of peasant households were there?
return peasant households ;return #1 in  1918 ;return #1 in  1920 ;return number of  #2 ;return number of  #3 ;return difference of #5 and  #4 in  millions
['select', 'filter', 'filter', 'aggregate', 'aggregate', 'arithmetic']