A group of firms that explicitly agree to coordinate price and output to act jointly like a monopoly is called a:

1. A cartel is an explicit agreement among firms to coordinate their activities. 2. By colluding on price and output they behave like a single monopoly. 3. This raises joint profit, especially when demand is inelastic. 4. OPEC is a well-known example of such a cartel. _Source: ICAI BoS CA Foundation Paper 4 Business Economics, Ch 4 Unit III "Price-Output Determination under Different Market Forms", p.27_