本研究分別採用成本效益分析法及實質選擇權方法建構兩個模型，用以進一步求算在社會福利極大化下，部份民營化之公股釋出最適比例與最適時機。
公營事業在民營化過程中，將有三種社會福利的影響：消費者剩餘之變動、民營後事業體績效提昇之影響及政府售出股權之收入影響。而其中民間持股與剩餘公股比例之結構，直接影響該事業體經營績效的提昇與否；因此，本研究建構已釋出公股、擬釋出公股比例與成本比率降低額的函數關係，並透過政府資金乘數與私人資金乘數將三種影響轉換成對社會福利的變動值；據此可以推導出民營化事業體在各已釋出公股比例、稅後盈餘與目前股價下，得出該階段擬釋出的最適比例。由本研究模型推論結果，可以得出一個估算公股最適釋出比例的模式與判斷再釋股與否的準則。
另外，本研究在模式化民營後績效改善程度的不確定性、股價不確定性及公司營業收入的不確定性，並透過複合彩虹選擇權的概念，建構可找出最適釋股時機的實質選擇權模式。
透過中華電信、中國鋼鐵等案例的試算亦證實這兩個模式的可應用性。輔以釋出公股決策準則的判斷，決策者可以得到在目前股價下是否應繼續釋股、釋出多少比例、何時釋出等答案。政府可以依此模式，先行預估完全民營後技術效率的改善程度，便可按上述步驟得出釋股與否與釋股最適比率幅度，作為民營化政策之參考。
同時我們發現：(1) 釋股的關鍵在於釋出價格與釋出後期待的效率增進間的相對大小，這兩因素間的抵換關係使得在釋股過程得以存在一個最釋比例。(2) 公營事業民營化除了股權移轉的過程外，尚須輔以移轉後的企業改革與管理等相關的永續計劃，當下釋股才具有未來正當性的基礎。公股管理得視產業實際狀況，政府應有售出、延後售出、事業體組織重整等的多重考量。綜合言之，在不同階段的公股管理，政府宜依社會福利考量，客觀地評量其民營化決策。

This study adopts the cost-benefit analysis method and the real option method to construct two models, and further determines under the maximization of social welfare, the optimal ratio and time of state-owned stock floatation for public enterprises undergoing partial privatization.
A public enterprise, during the process of privatization, will have three effects on social welfare: change in consumer surplus, improvement in business performance after privatization, and change in fiscal revenue when the government sells the stock holdings. A public enterprise, during the process of privatization, will have three effects on social welfare: change in consumer surplus, improvement in business performance after privatization, and change in fiscal revenue when the government sells the stock holdings. The study transfers the three effects on social welfare through the shadow multiplier on government funds and the shadow multiplier on private funds into the effect on social welfare. In light of this, the optimal ratio of state-owned stock floatation in different stages can be inferred under released public shares, after-tax income and current share price for privatized enterprises.
Moreover, after modeling three uncertainties from improved performance’s degree of the privatized enterprise, the stock price and the operating revenue, the study constructs the real option model. Using the model, the optimal floatation timing of state-owned stock can be found.
Through the calculation of case examples which the Chunghwa Telecom Company and China Steel Corporation, the applicability of such two models can be verified. It is also conducted the criterion of the released public shares, the policy-maker could obtain the answer under the current stock price whether the released public shares should be carried on, how many proportions should be released, when it be released. Through this model, the government could estimate the improvement degree of the technical efficiency after privatization in advance, pursuant to the above-mentioned procedure to make a decision whether state-owned stock is released or not and the range of the optimal ratio. It takes reference for the policy of the privatization
Two additional findings are: 1) The key to stock floatation lies in the relative proportion of release price to the expected increase in efficiency after release. The trade-off relationship between these two factors reserves the existence of one optimal ratio during the stock floatation process. 2) For public enterprise privatization, in addition to the share ownership transfer process, a sustainable plan that acts like an aid for enterprise reform and management after the transfer is necessary. Such a plan will play an important role for future justification of current stock floatation. The government should consider the multiple facets of selling, delayed selling, and enterprise reorganization. In summary, for the management of public shares at different stages, the government should objectively evaluate its decision of privatization by taking into account the social welfare changes.

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