為什麼建構網絡式組織是一個良好的策略，讓企業在高科技產業中有競爭優勢？本文先將引介一些組織理論家的理論，不過這些理論都是從個體廠商經營效率的觀點提出解釋，AnnaLee Saxenian則另闢蹊徑，其觀察重點在於一個交易系統的集體效率（collective efficiency）問題上。本文就是秉承著這個集體效率觀點研究網絡式組織的競爭優勢，一方面以人際關係網絡方法（network approach）進一步為AnnaLee Saxenian的實証觀察提出更深入的解釋，另一方面則提出集體效率的另一個重要面向--交易網絡的交易效率問題。本文先以Granovetter的「弱聯帶優勢」理論，解釋了Saxenian所觀察到，矽谷在知識擴散，新產品研發以及工業標準的設定上具有優勢，同時以「弱聯帶優勢」理論演申出來的Burt的「網絡間隙」理論，解釋了Rogers and Larsen觀察到矽谷的創業投資特別興盛，而且常在非正式場域中展開與進行。接下來本文以交易網絡的「相變」現象，佐以Granovetter的「鑲嵌」理論，解釋了為什麼網絡式組織在不穩定的市場中具有較高的交易效率。從而本文論証了矽谷作為一個主要由網絡式組織組成的產業環境，在知識擴散與交易效率上，比 128 公路區那種單兵作戰環境，較具競爭優勢。本文的論點與小企業與網絡式組織的理論，不同之處在於後者著眼在個別組織或一群相關組織的個體層次研究上，本文則置重點於組織所組成的產業環境或交易系統上，偏向總體層次的分析。這也正是Saxenian 研究HP為什麼擊敗DEC時，不以HP的策略聯盟擊敗了DEC的單兵戰鬥作為解釋，反而把問題置於整個產業環境中去探討，問出了矽谷為什麼擊敗128公路區這樣的問題，並回答是網絡式組織組成的產業環境擊敗了獨立公司與自由市場組成的產業環境。本文的目的正是要提醒組織學者，不要只集中注意力在個別組織的效率問題上，而應該以結構的觀點，看看不同組織型態構成的地區產業環境是否有效率。

　　　　　Taking a different approach from flexible-specialization theories, which emphasize firm-level advantages, collective efficiency offers another explanation for the competitive edge of network organizations. In answering why Hewlett-Packard Company (HP) surpassed Digital Equipment Corporation (DEC), Saxenian (1994) attributed it not to micro-level managerial or strategic factors, but rather to macrolevel regional advantage. In a comparison of the development trajectories of Silicon Valley (where HP is based) and Route 128 (wherre DEC is based), Saxenian attributed the success of Silicon Valley to its different style of doing business--namely, forming subcontracting networks and alliances, rather than building a vertically integrated bureaucratic structure in an environment of free competition. A widely accepted explanation for regional collective efficiency points to the effect of knowledge diffusion, that is stated in the first half of this paper. The influence of informal relationship networks to information flow has been observed by Granovetter's theory "The Strength of Weak Ties". Everett Rogers also realized how important diffusion networks are in adopting new innovations, and thus keeping regional technology state-of-the-art. He attributes the flourishing of diffusion networks in Silicon Valley to the high-frequency of personal interaction there, which facilitates inter-professional and inter-disciplinary communication. Saxenian also pointed out the importance of Silicon Valley's social life, city design and professional associations in encouraging such to its personal interaction, which in turn often stimulates knowledge exchange and entrepreneurship in the informal arena. Such networking among corporations helps to build a vibrant diffusion network. When and how is a subcontracting network preferable to a system composed of independent firms and free competition? This paper in the second half seeks to address this question in light of the studies done on organizational collective efficiency. By combining two theories--namely phase-transition in networks and embeddedness view of transaction costs--I aim to demonstrate when and how network organizations offer greater transaction efficiency than free competition among independent firms. This is an explanation of collective efficiency based on the studies of transaction cost.