在過去許多研究網路瀏覽行為的文獻中可以發現，絕大多數的網路瀏覽者會集中在少數幾個網站，這個現象符合Power law的觀念，同時亦可用80/20法則來描述此現象，即80%的瀏覽者的瀏覽次數集中於20%的網站，或80%的網站參觀次數是由20%的使用者創造。而本研究欲做更近一步的研究，採用集中度指標估算使用者及網站流量的集中程度，並以瀏覽頁數(Pageviews)、瀏覽時間(Duration)、造訪次數(Visits)三個變數觀察使用者及網站的集中情形，並進一步採用迴歸分析方法，探討網站集中度是否會受到哪些變數的影響。
本研究所分析的資料為民國九十二年十月份單月的網路流量資料，最後採用Gini指標做集中度的策量指標，研究發現：
(1) 平均每個網站有36.2個人參觀，平均被造訪的次數為235.8次，平均總瀏覽頁數為1049.4頁，平均瀏覽時間為6.08分鐘。
(2) 在使用者部分：Gini(Pageviews)的平均值為0.7545，Gini(Visits)的平均值為0.561，Gini(Duration)的平均值為0.7776；在網站部分：Gini(Pageviews)的平均值為0.534，Gini(Visits)的平均值為0.4089，Gini(Duration)的平均值為0.6319。
(3) 迴歸分析的結果發現，Gini指標與網站的網路流量有高度的相關性。

Abstract
Several early studies had found that most users’ browsing behavior were concentrated in a minority of website(s). This phenomenon related with power-law and 80/20 rule, e.g, 80 percent of the users’ browsing behavior concentrated in 20 percent of websites, or 20 percent of the users account for 80 percent of the website’s flow. This paper proposes concentration index to measure the degree of users’ and websites’ concentration in the browsing behavior and discuss this issue further. Finally, I use the regression analysis to find out which variable(s) could influence the Gini index of page views, visits, duration.
This research adopted one month (Oct. 2003) data to discuss. The findings are as follows:
(4) The average visitor of each website was 36.2, the average visits of each website was 235.8, the average page views of each website was 1049.4, the average duration of each website was 6.08 min。
(5) The part of users：the average of Gini(Pageviews) is 0.7545, the average of Gini(Visits) is 0.561, the average of Gini(Duration) is 0.7776. The part of websites：the average of Gini(Pageviews) is 0.534, the average of Gini(Visits) is 0.4089, the average of Gini(Duration) is 0.6319。
(6) Regression analysis：the Gini’s indexes of page views, visits, duration are related with the website flow, e.g, the number of page vies, the frequency of visits, the time of duration and the number of user.

Key word: Concentration, Concentration Index, Gini Index, Browsing Behavior

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