Final answer:
A successful campaign that decreases the supply of illegal drugs will increase their price and could potentially decrease the total amount spent on them, especially if the demand is elastic.
Step-by-step explanation:
A successful campaign that decreases the supply of drugs will increase the price of illegal drugs and decrease the total amount spent on them. This is because a reduced supply tends to drive up prices due to scarcity, while the higher prices may lower the quantity demanded, thus potentially reducing the total expenditure on the drugs, assuming that the demand is elastic.
An example of this principle can be seen in the case of cigarette consumption. Anti-smoking campaigns can shift demand to the left, decreasing the consumption of cigarettes, especially if the demand is elastic, as it appears to be particularly among youth. If such campaigns or policies make drugs less available or undesirable, this can impact both price and total spending similarly.