Longitudinal data is typical related data, and it is desirable to choose correct data variance structure since the correct structure affects the efficiency of estimation.

纵向数据为典型的相关数据，数据方差结构选择的正确与否直接影响估计的效率。

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The larger your data set the more variance you expect to have in your data set.

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The figures represent a variance from the previous data of 0.3 which sits right at the norm for annual benchmark adjustments which are typically up or down by 0.3 percent.

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