本研究中，考慮連續時間下，附最低保證之長期最適投資策略；在利率模型中，為較能符合現實狀況，我們採用CIR模型；另外，在此策略中，我們將投資人之風險偏好加入模型中研究，最適化投資人到期時財富之效用函數，並用Cox & Huang之市場中立評價方法來解決數學模型問題。此篇研究顯示，最適之投資策略可以等價於某些共同基金之投資組合，這些共同基金能利用金融市場上之主要資產(market primary assets)來複製。 / In this study, we consider a portfolio selection problem for long-term investors. Dynamic investment strategy with the continuous-time framework incorporating the minimum guarantees are constructed. Maximizing expected utility of the terminal wealth is employed by investors to trade off profits in good future state against losses incurred in worse states. Follow the previous works of Deelstra et al. (2003), we concentrate on the simplest case of a one-factor Cox-Ingersoll-Ross (CIR) model in formulating the stochastic variation from the interest rate risks. Under the market completeness assumption, the fund growth is modelled under the market neutral valuation and the optimal rules are mapped into the static variational problem of Cox and Huang (1989). In this study, we show that the optimal portfolio is equivalent to a certain mutual fund that can be replicated by the market primary assets

<p>Pension fund companies manage and invest large amounts of money on behalf of their members. In return for their contributions, members expect a benefit at termination of their contract. Due to the volatile nature of returns that pension funds attain, pension companies started attaching a minimum guaranteed amount to member&rsquo / s benefits. In this mini-thesis we look at the pioneering work of Brennan and Schwartz [10] for pricing these minimum guarantees. The model they developed prices these minimum guarantees using option pricing theory. We also look at the model proposed by Deelstra et al. which prices minimum guarantees in a stochastic financial setting. We conclude this mini-thesis with new contributions where we look at simple alternative ways of pricing minimum guarantees. We conclude this mini-thesis with an approach, related to the work of Brennan and Schwartz [10], whereby the member&rsquo / s benefit is maximised for a given minimum guaranteed amount, which comprises of multi-period guarantees. We formulate a method to find the optimal stream of these multi-period guarantees.</p>

<p>Pension fund companies manage and invest large amounts of money on behalf of their members. In return for their contributions, members expect a benefit at termination of their contract. Due to the volatile nature of returns that pension funds attain, pension companies started attaching a minimum guaranteed amount to member&rsquo / s benefits. In this mini-thesis we look at the pioneering work of Brennan and Schwartz [10] for pricing these minimum guarantees. The model they developed prices these minimum guarantees using option pricing theory. We also look at the model proposed by Deelstra et al. which prices minimum guarantees in a stochastic financial setting. We conclude this mini-thesis with new contributions where we look at simple alternative ways of pricing minimum guarantees. We conclude this mini-thesis with an approach, related to the work of Brennan and Schwartz [10], whereby the member&rsquo / s benefit is maximised for a given minimum guaranteed amount, which comprises of multi-period guarantees. We formulate a method to find the optimal stream of these multi-period guarantees.</p>

Magister Scientiae - MSc / Pension fund companies manage and invest large amounts of money on behalf of their members. In return for their contributions, members expect a benefit at termination of their contract. Due to the volatile nature of returns that pension funds attain, pension companies started attaching a minimum guaranteed amount to member&rsquo;s benefits. In this mini-thesis we look at the pioneering work of Brennan and Schwartz [10] for pricing these minimum guarantees. The model they developed prices these minimum guarantees using option pricing theory. We also look at the model proposed by Deelstra et al. which prices minimum guarantees in a stochastic financial setting. We conclude this mini-thesis with new contributions where we look at simple alternative ways of pricing minimum guarantees. We conclude this mini-thesis with an approach, related to the work of Brennan and Schwartz [10], whereby the member&rsquo;s benefit is maximised for a given minimum guaranteed amount, which comprises of multi-period guarantees. We formulate a method to find the optimal stream of these multi-period guarantees. / South Africa

>Magister Scientiae - MSc / Pensions are essentially the only source of income for many retired workers. It is thus critical that the pension fund manager chooses the right type of plan for his/her workers.Every pension scheme follows its own set of rules when calculating the benefits of the fund’s members at retirement. Whichever plan the manager chooses for the members,he/she will have to invest their contributions in the financial market. The manager is therefore faced with the daunting task of selecting the most appropriate investment strat-egy as to maximize the returns from the financial assets. Due to the volatile nature of stock markets, some pension companies have attached minimum guarantees to pension contracts. These guarantees come at a price, but ensure that the member does not suffer a loss due to poorly performing equities.In this thesis we study four types of mathematical problems in pension fund management,of which three are essentially optimization problems. Firstly, following Blake [5], we show in a discrete time setting how to decompose a pension benefit into a combination of Euro-pean options. We also model the pension plan preferences of workers, sponsors and fund managers. We make a number of contributions additional to the paper by Blake [5]. In particular, we contribute graphic illustrations of the expected values of the pension fund assets, liabilities and the actuarial surplus processes. In more detail than in the original source, we derive the variance of the assets of a defined benefit pension plan. Secondly,we dedicate Chapter 6 to the problem of minimizing the cost of a minimum guarantee included in defined contribution (DC) pension contracts. Here we work in discrete time and consider multi-period guarantees similar to those in Hipp [25]. This entire chapter is original work. Using a standard optimization method, we propose a strategy that cal- culates an optimal sequence of guarantees that minimizes the sum of the squares of the present value of the total price of the guarantee. Graphic illustrations are included to in-dicate the minimum value and corresponding optimal sequence of guarantees. Thirdly, we derive an optimal investment strategy for a defined contribution fund with three financial assets in the presence of a minimum guarantee. We work in a continuous time setting and in particular contribute simulations of the dynamics of the short interest rate process and the assets in the financial market of Deelstra et al. [19]. We also derive an optimal investment strategy of the surplus process introduced in Deelstra et al. [19]. The results regarding the surplus are then converted to consider the actual investment portfolio per- taining to the wealth of the fund. We note that the aforementioned paper does not use optimal control theory. In order to illustrate the method of stochastic optimal control, we study a fourth problem by including a discussion of the paper by Devolder et al. [21] in Chapter 3. We enhance the work in the latter paper by including some simulations. The specific portfolio management strategies are applicable to banking as well (and is being pursued independently).

已開發國家中，無論個人或是法人所擁有之財富大多透過金融中介機構管理，因此，財富委由他人管理衍生出現代資本市場中重要的委託關係。委託人與基金管理人產生委任契約時，也必然產生代理問題，即雙方利益不一致所額外增加的成本。為降低代理成本，於委任合約加入對管理人下檔投資風險的要求成為降低代理成本的重要機制。本研究因此探討當基金管理人面對契約存在最低報酬要求時，如何進行最適資產配置決策，並同時分析下檔風險限制改變時對管理人投資行為的影響。研究結果顯示，委任合約增加經理人最低保證收益時，基金管理人傾向增加持股，而經理人風險趨避程度增加時，將減少風險性股票資產，進而持有債券；如果投資目標收益於受委託期間皆不改變，將造成經理人持有債券組合以規避下檔風險，同時卻喪失追求資本利得。 / In most developed countries, financial wealth is not managed directly by the investors, but through a financial intermediary. Hence, the delegated portfolio management is one of the most important principal-agency relationships in the current economy. In addition to that, the principal-agency relationships between the investor and portfolio manager must produce agency cost. In order to reduce these costs, the mandates in the contract become an important factor in reducing the principal-agent problem in a delegated portfolio management framework. In this research, we study how fund managers do asset allocation when they face some guaranteed returns and the relationships between the choices of mandates and the behavior of fund managers. We suppose that the objective of the delegated fund managers is to maximize the expected utility of wealth of the long-term fund at the end of each period and fund managers also have to fulfill some constrains given at the beginning. Finally, we explain how fund managers do optimal asset allocation by our model and some numerical analysis.