Perfect competition	monopolistic competition	oligopoly	monopoly
number of firms	many	many, too many for collusion	few, collusion is possible	one
monopoly power	none, firms are price takers	very limited	expanded	total
ease of entry / exit	yes, no barriers to entry or exit	yes, no barriers to entry or exit	no, significant barriers to entry and exit (rent seeking)	no, significant barriers to entry and exit (rent seeking)
product	homogenous	heterogeneous	homogenous or heterogeneous	unique
concerns about other firms in the market	no, perfect information	yes, because they need to advertise to keep market share	yes, mutual interdepence exists as does the possibilities for collusion	no, there are no other firms
demand elasticity	perfectly elastic	highly elastic	kinked	highly inelastic
types of information	perfect	imperfect, but you can acquire info at a low cost	imperfect, and can become a barrier to entry	imperfect and is a barrier to entry
exploitation	no, P = MC (allocative efficiency)	yes but slight	yes more monopoly power than Mono Comp	yes and also discrimination is possible
profits	short run only	short run only	both long and short run	both long and short run
efficient production	yes forced cost minimization (productive and allocative efficiency)	no, excess capacity exists and there is no allocative efficiency	no, excess capacity exists and there is no allocative efficiency	no, excess capacity exists and there is no allocative efficiency
advertising	no	yes, persuasive	yes, persuasive and goodwill	yes, goodwill