cities are self-organizing systems. Credibility thesis suggests that the credibility of social institutions is the driving factor behind the endogenous self-organization of institutions and their persistence. Different rules of game would cause different types of spontaneous order. If an economic society obeys the equal-opportunity rules, the resulting spontaneous order is reflected as an exponential income distribution; that is, for an equal-opportunity economic society, the exponential income distribution is most likely to evolve and survive. By analyzing datasets of household income from 66 countries and Hong Kong SAR, ranging from Europe to Latin America, North America and Asia, Tao et al found that, for all of these countries, the income structure for the great majority of populations (low and middle income classes) follows an exponential income distribution. Criticism Roland Kley writes about Hayek's theory of spontaneous order that "the foundations of Hayek's liberalism are so incoherent" because the "idea of spontaneous order lacks distinctness and internal structure." The three components of Hayek's theory are lack of intentionality, the "primacy of tacit or practical knowledge", and the "natural selection of competitive traditions." While the first feature, that social institutions may arise in some unintended fashion, is indeed an essential element of spontaneous order, the second two are only implications, not essential elements. Hayek's theory has also been criticized for not offering a moral argument, and his overall outlook contains "incompatible strands that he never seeks to reconcile in a systematic manner." See also Anonymous Deregulation Emergence Free price system "I, Pencil" by Leonard Read Mutual aid Natural law Natural order Revolutionary spontaneity Stigmergy Tragedy of the commons Wu wei (Effortless Action) References Systems theory Self-organization Austrian School Libertarian theory Pattern formation