Since the Price of Anarchy is the ratio of the best possible strategy to the worst Nash equilibrium PoA(G)=maxs∈S∑i∈Nui(s)mins∈NE(G)∑i∈Nui(s) and the Price of Stability is the ratio of the best possible strategy to the best Nash equilibrium PoS(G)=maxs∈S∑i∈Nui(s)maxs∈NE(G)∑i∈Nui(s), one could define the Price of Inadequacy as either the difference between the two PoI(G)=PoA(G)−PoS(G) or as the ratio between the two PoI(G)=maxs∈NE(G)∑i∈Nui(s)mins∈NE(G)∑i∈Nui(s).
Since the Price of Anarchy is the ratio of the best possible strategy to the worst Nash equilibrium PoA(G)=maxs∈S∑i∈Nui(s)mins∈NE(G)∑i∈Nui(s) and the Price of Stability is the ratio of the best possible strategy to the best Nash equilibrium PoS(G)=maxs∈S∑i∈Nui(s)maxs∈NE(G)∑i∈Nui(s), one could define the Price of Inadequacy as either the difference between the two PoI(G)=PoA(G)−PoS(G) or as the ratio between the two PoI(G)=maxs∈NE(G)∑i∈Nui(s)mins∈NE(G)∑i∈Nui(s).