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The problem of environmental pollution is rampant around the globe with the passage of time. Here, we take up water pollution seen at Lake Biwa located in Shiga Prefecture in Japan. A few decades has passed since the water pollution of the lake became a topic. Many people who live in Kyoto and Osaka areas highly depend on their water in the lake. If we take contaminated water and fish periodically, our heath will be destroyed gradually. The serious problem is that some materials which cause cancer are included. Thus, we must show some prescription to provide for the safe water and maintain the fishing volume in the lake. Basically, this analysis is based on the models of liner first order differential equations made up by the author. At first, we show the mechanism how this kind of pollution occurs. Generally speaking, many causes are considered including contaminated materials discharged by houses and factories, etc. adjacent to the lake. Time series analysis is taken into consideration to indicate the pollution mechanism. Secondly, we show the decline of fishing volume in the lake. Intuitively, we can imagine the negative correlation between water pollution and fishing volume. Namely, if the water pollution be serious, the fishing volume would decline. Furthermore, we refer to the metamorphosis of ecosystem in the lake. Thirdly, we show the status quo of the lake and how administrative sides tackle this problem. Fortunately, the water pollution of the lake is diminishing and fishing volume is increasing due to the efforts of the parties concerned. However, it seems there needs more improvement to reach the satisfactory level. Finally, we show a future perspective to resolve this problem smoothly by indicating the concrete examples.

When we consider pension fund management, asset only approach is traditionally used for optimal asset allocation. Recently, optimal asset allocation based on surplus framework is noteworthy. So, we investigate the feature of optimal asset allocation under the consideration of both asset and liability in pension fund. There are two surplus approaches such as ALM and LDI. We use mainly ALM approach which is often called as a balance sheet type ALM. Because, we apply this idea for Japanese government pension fund and the plan yield is given as 3.2 percent by Japanese government. However, the mainstream of pension fund management in U.K., Holland, and Denmark, etc. is LDI. The concept of LDI is also accepted and executed by the U.S.A.. So, we apply LDI’s idea into this analysis. Namely, we execute the simulations by changing the volatility of liability and notice the difference of efficient frontier in both surplus and asset only approaches. Thus, as we increase the surplus return, the asset allocation of higher risk assets will increase and also increase the surplus risk simultaneously.

We select the top four hedge fund strategies as desirable ones based on the Prospect Ratio in this paper, and we examine the risk factors of each hedge fund strategy to specify the source of return in the past ten years. We use multifactor models based on GMM analysis. And we use AIC (Akaike Information Criterion) and SIC (Schwarz Information Criterion) to resolve the problem to specify the valid exogenous variables in each strategy. The result shows that the selected model contains only significant exogenous variables in each strategy.

After the devastating damages of East Japan Earthquake, we investigate the affection of supply in steel. There are several steel companies in Japan such as Nippon Steel Corporation, JFE Steel Corporation, Sumitomo Metal Industries, Ltd and Kobe Steel, Ltd. Namely, steel industries are mainly controlled these four companies. So, we grasp this status as “Oligopoly”. And we also mention this as a homogeneous oligopolistic market. Suppose that the supply level of Nippon Steel Corporation is decreased due to the earthquake. If this situation will occur, how will it affect another steel company's price of the same product? We use the concept of “Conjectural Variation” to resolve this problem. Conjectural variation means the volatility of another companies supply levels which Nippon Steel Corporation will conjecture when Nippon Steel Corporation will decrease (or increase) its supply level. Thus, if each company will determine its supply level to maximize its profit in a homogeneous oligopolistic market, the price level is written by the three factors such as elasticity of price, marginal cost and conjectural variation. Here, we add three suppositions. Firstly, price elasticity of a certain product is constant temporarily regardless of the total demand level. Secondly, marginal cost in each company is constant regardless of the production level within its production capacity. Thirdly, conjectural variation in each company is constant in each fiscal term. Based on former three suppositions, price will be determined prior to demand level. Finally, we investigate how conjectural variation's change will affect the price level. The result is that if a company's marginal cost is minimized, the increase (or decrease) of the company's conjectural variation will occur the increase (or decrease) of price level under the conditions that given another situations are equal.