The table below shows the four-firm concentration ratio of various industries.

 

Industry	Four-firm concentration ratio
Petroleum and coal products	34.1
Coffee and tea manufacturing	52.5
Cigarettes	98.9
Plastics and rubber product manufacturing	10.5
Aerospace product and parts	55.6

Which of the following industries is the closest to perfect competition?

The plastics and rubber products industry is the closest to perfect competition because it has the lowest four firm concentration ratio. The four firm concentration ratio for the plastics and rubber products industry is 10.5%. This shows that the largest firms in the plastics and rubber products market don't have enough market share to properly collude to restrict output and increase prices. If the firms are unable to collude, the reason that the industry is the closest to competition is because the market inefficiencies that occur from collusion are not as profitable as those in industries with stronger four firm concentration ratios.