Each of the six candidates below addresses a problem that has been described, formalized and in several cases recognized with a Nobel Prize — and then left unsolved. That pattern is worth examining before the candidates themselves, because it is the pattern that the paradigm explains.
In every case the problem was correctly diagnosed and no mechanism followed. Coase identified transaction costs, information asymmetries and externalities as the reason firms and regulation exist, and neither he nor Williamson, Ostrom, or Acemoglu, Johnson and Robinson supplied a way to dissolve them. Spence formalized costly signaling and the deadweight loss it imposes; the loss remained. Hayek argued that prices aggregate distributed knowledge no planner can hold, and no mechanism existed to make that aggregation operate outside conventional markets. Mundell and Fleming stated the monetary trilemma as a constraint, not a puzzle to be solved.
The common cause is substrate, not insight. Each of these frictions is a consequence of the same underlying limitation: a resource could not be used without being surrendered, governance could not survive recombination, and obligations could not propagate without an enforcer. Given those constraints, the frictions are not defects of institutional design but necessary features of any coordination system built on that substrate. Economics correctly described the equilibrium available under the constraints. What it could not do was change the constraints, because changing them required a construction rather than an analysis.