The Lee-Carter (LC) model has been recurrently used to forecast mortality, including by national statistical offices. This model has many advantages, but tends to underpredict life expectancy due to its assumption of constant age-specific response to the time index. Does this bias emerge from all ages or from specific ages only? In this paper, we aim to provide a more detailed evaluation of the model, by evaluating its accuracy, bias and robustness by age. Our analysis is based on 806 out-of-sample forecasts using various different fitting periods and forecast horizons. We focus on age 65 and above, as most deaths occur at older ages nowadays. We showed that the LC model is not fundamentally biased, but its main assumption of constant age-specific response to the time index, often leading to constant rates of mortality improvement, is not appropriate in all populations and at all ages.

Lee-Carter (LC) 模型经常被用于预测死亡率，包括国家统计局。该模型具有许多优点，但由于其假设对时间指数的特定年龄响应恒定，因此往往低估了预期寿命。这种偏见是来自所有年龄段还是仅来自特定年龄段？在本文中，我们旨在通过按年龄评估其准确性、偏差和稳健性，对模型进行更详细的评估。我们的分析基于使用各种不同拟合期和预测范围的 806 个样本外预测。我们专注于 65 岁及以上，因为现在大多数死亡发生在老年人身上。我们表明 LC 模型从根本上没有偏差，但它的主要假设是对时间指数的特定年龄响应恒定，通常导致死亡率提高率恒定，