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Path dependence explains how the set of decisions one faces for any given circumstance is limited by the decisions one has made in the past, even though past circumstances may no longer be relevant.〔Definition from ("Our Love Of Sewers: A Lesson in Path Dependence" ), Dave Praeger, 15 June 2008.〕 In economics and the social sciences, path dependence can refer either to outcomes at a single moment in time, or to long-run equilibria of a process. In common usage, the phrase implies either: * (A) that "history matters" — a broad concept, or * (B) that predictable amplifications of small differences are a disproportionate cause of later circumstances. And, in the "strong" form, that this historical hang-over is inefficient. The first usage, (A): "history matters" is trivially true in the explanatory context; everything has causes. And in these fields, the direct influence of earlier states isn't notable〔 The standard economic growth rate measurements are path-dependent, and "the phenomenon of dependence of history might be ignored for short period of time (10 years, 20 years), but is not negligible for secular comparisons."〕 (compare "path-dependent" options in finance, where the influence of history can be non-standard). It is the narrow concept (B), that has the most explanatory force, and which is covered in this article. ==Illustration== Consider as an example the videotape format war; Two mechanisms ''independent of product quality'' could explain how VHS achieved dominance over Betamax from a negligible early adoption lead: * A network effect: videocassette rental stores observed more VHS rentals and stocked up on VHS tapes, leading renters to buy VHS players and rent more VHS tapes, until there was complete vendor lock-in. * A VCR manufacturer bandwagon effect of switching to VHS-production because they expected it to win the ''standards battle''. An alternative analysis is that VHS was better-adapted to market demands (e.g. having a longer recording time). In this interpretation, path dependence had little to do with VHS's success, which would have occurred even if Betamax had established an early lead. Positive feedback mechanisms, like bandwagon and network effects, are at the origin of path dependence. They lead to a reinforcing pattern, in which industries 'tip' towards one or another product design. Uncoordinated standardisation can be observed in many other situations. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Path dependence」の詳細全文を読む スポンサード リンク
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