英文文献：Three-Dimensional Efficient Portfolio Frontier: Mean, Variance, and Farm Size-三维有效投资组合边界:均值、方差和农场规模
英文文献作者：Peterson, Hikaru Hanawa,Schurle, Bryan W.,Langemeier, Michael R.
英文文献摘要：
With continuing trends in increasing farm size and declining number, the impact of size of operation on risk may have significant policy implications. Diversification indexes for 288 Kansas farms from 1984 to 2003 indicated that sample farms had become slightly more diversified over time. Previous findings on the impact of farm size on diversification of farms have been controversial. To capture observed size impacts on enterprise-specific risks, a mean-variance model that allows for variance of enterprise returns to be decreasing in assets allocated is conceptualized. Efficient farm enterprise mixes are estimated using farm level data, showing that the optimal levels of diversification differ for farms of different sizes. For example, small farms should diversify more than large farms to achieve the same level of return. Results from a panel regression analysis showed that the relationship between farm size and diversification depended on how farm size was measured, reconciling the past findings.

随着农场规模不断扩大和数量不断减少的趋势，经营规模对风险的影响可能会产生重大的政策影响。1984年至2003年堪萨斯州288家农场的多样化指数表明，随着时间的推移，样本农场的多样化程度略有提高。以前关于农场规模对农场多样化影响的研究结果一直存在争议。为了捕捉观察到的规模对企业特定风险的影响，我们概念化了一个均值-方差模型，该模型允许企业收益的方差在资产分配中减少。利用农场水平的数据估计了有效的农场企业混合，表明多样化的最佳水平对不同规模的农场是不同的。例如，小型农场应该比大型农场更加多样化，以达到相同的回报水平。面板回归分析的结果显示，农场规模和多样化之间的关系取决于如何衡量农场规模，这与过去的发现相一致。