The desire to avoid pregnancy—to delay the next birth or have no further births—is a fundamental sexual and reproductive health indicator. We show that two readily available measures—prospective fertility preferences and the demand for contraception [Demand] construct—provide substantially different portraits of historical trends. They also yield correspondingly different assessments of the sources of contraceptive change. We argue, with supporting empirical evidence, that Demand enormously overstates the historical trend in the desire to avoid pregnancy because Demand as currently constructed is in part a function of contraceptive prevalence. This makes for “reverse causality” in decompositions of contraceptive change, producing an upward distortion on the order of 25 percentage points in the amount of contraceptive change attributed to a change in fertility desires. Decomposition of contraception change free of the distortion reveals that contraceptive change has been due almost entirely to more complete implementation of fertility preferences. This is explained in part by the surprisingly slight historical change in preferences, a fact we document and then show is a consequence of a historical shift in parity composition toward lower parities.

中文翻译：

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评估避孕意愿的趋势：警告


避免怀孕的愿望——推迟下一次生育或不再生育——是一个基本的性健康和生殖健康指标。我们表明，两种现成的衡量标准——预期生育偏好和避孕需求[需求]构建——提供了截然不同的历史趋势描述。它们还对避孕方法改变的来源产生了相应不同的评估。我们认为，在实证证据的支持下，需求极大地夸大了避免怀孕的历史趋势，因为目前构建的需求在一定程度上是避孕普及率的函数。这使得避孕方法改变的分解产生了“反向因果关系”，导致生育意愿变化导致的避孕方法改变量向上扭曲了约 25 个百分点。对避孕方法变化的分解（不存在扭曲）表明，避孕方法的变化几乎完全归因于更全面地实施生育偏好。这在一定程度上可以通过偏好历史上令人惊讶的微小变化来解释，我们记录并证明的这一事实是平价构成历史性向较低平价转变的结果。