question: Did more households have a car in 2015 or in 2016?
#1 return households in  2015 
#2 return households in  2016 
#3 return #1 that have a car 
#4 return #2 that have a car 
#5 return number of  #3 
#6 return number of  #4 
#7 return which is more of #5 ,  #6