| Perfect Competition | Imperfect Competition | |||
| Monopoly | Monopolistic Competition | Oligopsony | ||
| Number of firms | Many | One | Many | A few |
| Price Control | None | Full | Partial | partial |
| Commodity | Homogeneous | Unique | Differentiated | Unique or differentiated |
| Barriers to entry | None | Insurmountable | none | Significant |
| Information | Available to all | Not available | Limited | Strongly Limited |
| Economic profit | None in the long run | Always positive | Positive in the short run and zero in the long run | Positive or none |