Efficient portfolio is a portfolio that yields maximum expected return given a level of risk or has minimum level of risk given a level of expected return.However,the optimal portfolios seem not being as efficient as intended.Especially during financial crisis period.optimal portfolio is not an optimal investment as it does not yield maximum return given a specific level of risk,vice and versa.One possible explanion for an unimpressive performance of the seemingly efficient portfolio is incorrectness in parameter estimates called"estimation risk in parameter estimates".Five different estimating strategies are employed to explore ex post portfolio performance when estimation risk is incorporated.These strategies are traditional mean-variance(EV),Adjusted Beta(AB) approach,Capital Asset Pricing Model(CAPM),Single Index Model(SIM), and Single Index Model incorporating shrikage Bayesian factor namely Bayesian Single Index Model(BSIM).Among the five alternative strategies,shrinkage estimators incorporating the single index model outperforms other traditional portfolio selection strategies.Allowing for asset mispricing and applying Bayesian shrinkage adjusted factor to each asset's alpha,a single factor namely excess market return is adequate in alleviating estimation uncertainty. JEL：G320

股票间的关联性是组合投资分析的关键内容，然而金融方面的研究文献很少有直接关心股票收益率间的关联性。本文研究上证180指数样本股票的关联性，采用单指数模型、常量相关模型、历史相关矩阵方法和第一主成分指数方法等4种预测方法，预测股票的相关矩阵，发现在单、双周收益率下，无论是统计意义下还是经济意义下的检验，常量相关模型的预测效果最好，而历史相关矩阵方法最差。此外，股票间的相关性是时变的。这些发现对中国股票市场的组合投资分析有重要的参考价值。