自民國91年，國內法令准許私募，私募是指公司的內部人，透過協商，尋求願意投資公司的投資人，把公司的股票，售給少數的投資人，不需經過承銷商，揭露也比較少。
國外的文獻，有些學者實證的結果，私募宣告時有正的異常報酬，但有些學者實證的結果發現有負的異常報酬，本篇主要探討國內宣告私募時，對公司價值的影響，以及國內公司大多屬於家族企業，在這麼高的控制權之下，股權集中度對於私募發行公司的價值又有什麼影響？
實證的結果發現，國內公司宣告私募時有正的異常報酬，除了資訊不對稱會影響公司價值之外，本文還發現，公司在私募時，家族集團的控股如果低於30%時，增加公司持股，可以增加公司的價值，但當家族集團的股權超過30%時，就不明顯了。
此外，當股權集中度在10%~30%時，公司價值的變化與股權集中度成反比，顯示國內股權集中度在10%~30%時，符合利益掠奪假（Entrenchment Hypothesis），增加公司的股權集中度反而會減少公司的價值。

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