Question

which two of the following is a positive externality fewer students get measles because all students are required to have the mmr vaccine as the dropout rate decrease, so did crime. xyz corporation pollutes the river when they produce their product. the increased industrialization of china has led to an increase in smog in the cities

Explanation:

A positive externality is a benefit that is enjoyed by a third - party who did not directly pay for it.

• For the option "Fewer students get measles because all students are required to have the MMR vaccine": When all students get the MMR vaccine, not only do the vaccinated students benefit from being less likely to get measles, but other students (who may not have been vaccinated for some reason or are in the same environment) also benefit from herd immunity, which is a positive externality.
• For the option "As the dropout rate decrease, so did crime": A decrease in the dropout rate is an action (maybe due to better education policies etc.), and the decrease in crime is a benefit that society (third - parties) gets from the lower dropout rate, so this is also a positive externality.
• The option "XYZ Corporation pollutes the river when they produce their product" is a negative externality as it imposes a cost (pollution) on third - parties (people who use the river etc.).
• The option "The increased industrialization of China has led to an increase in smog in the cities" is also a negative externality as it imposes a cost (smog - related health issues, reduced air quality etc.) on third - parties.

Answer:

• Fewer students get measles because all students are required to have the MMR vaccine
• As the dropout rate decrease, so did crime.