本論文主要研究地理多角化與資訊透明度對公司權益資金成本的影響。主要資料均來源於DataStream資料庫及與其整合的I/B/E/S資料庫。最後，通過合併所有變量及刪除異常值，我們共採用了7934個全球樣本，時間跨度為2002年至2013年。
結果顯示，公司進行地理多角化會顯著增加其權益資金成本。這表明進行多角化的公司，其獲得的好處小於所付出的成本。也從另一層面提醒欲進行多角化的公司應在各個方面完善自身的管理。隨後，我們探討了資訊透明度是否會對多角化公司的權益資金成本有所減低。首先我們研究了公司的審計事務所為四大是否會比公司的審計事務所為非四大有所降低。結果表明，不管是從截距角度還是斜率角度，四大的客戶均有相對較低的權益資金成本，但顯著性水平并不太高，但至少表明有這種趨勢。接著，我們進一步檢驗四大且產業專長，四大非產業專長與非四大非專長的審計公司對其審計客戶的權益資金成本的影響。結果四大非產業專長從截距與斜率角度均顯著降低公司權益資金成本，但四大且產業專長的事務所卻不顯著。出現這樣的結果可能是因為產業專長分類上的一些限制造成的。不過從我們的實證結果來看，至少四大相對於非四大有降低多角化公司權益資金成本的趨勢。

This paper is mainly a study of geographic diversification and information transparency on firm cost of equity capital. Our primary data are all from the DataStream database and the I/B/E/S database. After merging all the variables and deleting any abnormal values, we ultimately have 7,934 firm-year observations from 2002 to 2013 globally.
Our first regression results showed that geographic diversification will increase the cost of equity capital. This indicates that the benefits of diversified companies are less than the costs. It also reminds diversified firms to improve their managerial skills in order to benefit more. Next, we examine whether information transparency can reduce the cost of equity capital. The results show that the clients of Big 4 audit firms enjoy a reduction on cost of equity capital compared to the clients of non-Big 4 audit firms. The level of significance is not high enough, but at least it reveals this reduction trend. Then, we make further study on the Big 4 but not industry specialist and both Big 4 and industry specialist to see if there are any differences. To our surprise, clients of Big 4 but not industry specialist audit firms enjoy a significant reduction on the cost of equity while the reduction for clients of Big 4 and also industry specialist audit firms is not significant. The classification limits on industry specialists may have caused these results.
All in all, from our empirical results, a trend was found indicating that the clients of Big 4 audit firms enjoy a reduction in the cost of equity.

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