Due to the higher costs and selection bias of directly measuring weight, the majority of body weight data are based on survey responses. However, these statements are subject to systematic biases of social desirability; therefore, it is important to evaluate the magnitude of bias through indirect indicators such as rounding of weights. Data from seven rounds of the Spanish National Health Survey from 1995 to 2017 were included in the study, with 113,284 subjects. A general rounding index of weights terminating in 0 and 5, and a partial rounding index that estimated the bias direction, were used to estimate the bias distribution in the self-reporting of body weight. All body weights were systematically rounded, although more strongly in the lower weights and even more so in the higher weights. Lower weights were rounded up, and the higher weights rounded down. Regarding gender, men had higher rounding indices than women. The subjects generally reported a weight closer to the socially desirable weight. Rounding allows estimating the historical evolution of this bias in health and nutrition surveys, having more accurate information by population segments and designing public policies against obesity aimed at the more affected social segments.

中文翻译：

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四舍五入作为健康调查报告体重偏差的指标

由于直接测量体重的成本较高和选择偏倚，大多数体重数据都是基于调查结果。然而，这些陈述受制于社会期望的系统性偏见；因此，重要的是通过权重四舍五入等间接指标来评估偏差的大小。该研究纳入了 1995 年至 2017 年七轮西班牙国家健康调查的数据，共有 113,284 名受试者。以0和5结尾的权重的一般舍入指数和估计偏差方向的部分舍入指数用于估计体重自我报告中的偏差分布。所有体重都被系统地四舍五入，尽管在较低的重量中更强烈，在较高的重量中更是如此。较低的权重被四舍五入，较高的权重向下舍入。关于性别，男性的四舍五入指数高于女性。受试者通常报告的体重更接近社会期望的体重。四舍五入可以估计健康和营养调查中这种偏见的历史演变，获得更准确的人口群体信息，并针对受影响更大的社会群体设计针对肥胖的公共政策。