Al believes that SUVs have negative social and environmental effects because of their increased carbon monoxide emissions. He proposes eliminating sales taxes on smaller automobiles in favor of higher sales taxes levied on SUVs. Al performs some calculations and comes to the conclusion that based on the current number of SUVs owned in the US, exactly the same amount of total sales tax will be collected under his reformed system. Which of the following concepts explains why Al's idea may not work? Multiple Choice The ability to pay principle Horizontale Substitution effect Vertical equity None of the choices are correct