The parametric model introduced by Lee and Carter in 1992 for projecting mortality rates in the US has been a seminal development and has been widely used since then. Different versions of the model, incorporating constraints on the data, and different adjustment methods have led to improvement. All of these changes have increased the complexity of the model with a corresponding improvement in goodness of fit, however, there is little change in the accuracy of forecasts of life expectancy in comparison with the original Lee-Carter model, according to some authors.
To evaluate to what point the increments in the complexity and computational cost of the models are reflected in the forecast of such indices as life expectancy and modal age at death, among others, we have compared three different models: the original Lee-Carter with one parameter and the Lee-Carter model with two temporal parameters forecasted by means of two independent time series or by means of a bivariate one. The three sets of predictions so obtained are compared using a mixture of block-bootstrap techniques and functional data analysis.