Centre for Population Change and Division of Social Statistics, University of Southampton, UK.
Demography. 2011 Aug;48(3):841-61. doi: 10.1007/s13524-011-0033-4.
Tempo effects in period fertility indicators are widely regarded as a source of bias or distortion. But is this always the case? Whether tempo change results in bias depends, in the view advanced here, on the measure used, the meaning of bias/distortion, and the objective of analysis. Two ways of construing bias in period measures are suggested, and their relevance is discussed in the context of five broad purposes for measuring period fertility: describing and explaining fertility time trends, anticipating future prospects, providing input parameters for formal models, and communicating with nonspecialist audiences. Genuine timing effects are not biasing when period fertility is the explanandum but are distorting when the aim is to estimate cohort fertility. Alternatives to tempo adjustment are available that are a more defensible solution to the issue of timing change. Tempo adjustment could be more fruitfully considered a form of modeling rather than empirical measurement. The measurement of period fertility could be improved by relying more on a statistical approach and less on indicators based on stable assumptions. Future progress will depend on integrating research on measurement with substantive investigation.
时期生育指标中的时变效应被广泛认为是产生偏差或扭曲的原因。但情况是否总是如此呢？本文认为，时变是否会导致偏差取决于所使用的度量标准、偏差/扭曲的含义以及分析的目的。本文提出了两种解释时期测量中偏差的方法，并在衡量时期生育的五个广泛目的的背景下讨论了它们的相关性：描述和解释生育时间趋势、预测未来前景、为正式模型提供输入参数以及与非专业受众沟通。当时期生育率是解释变量时，真正的定时效应不会产生偏差，但当目的是估计队列生育率时，它们会产生扭曲。有一些替代时间调整的方法，它们是解决时间变化问题的更合理的解决方案。时间调整可以更有效地被视为一种建模形式，而不是经验测量。通过更多地依赖基于统计方法而不是基于稳定假设的指标，可以改进时期生育率的测量。未来的进展将取决于将测量研究与实质性研究相结合。
