rivista italiana di economia demografia e statistica - Sieds

8
Volume LXV n. 1 – Gennaio-Marzo 2011
. (4)
Being model (4) identical to model (2), except for the R parameter that has been
added to the second component, it is clear that, by construction, it cannot perform
worse; but how better can it do at the cost of one more parameter? As it can be seen
from Table 1, for the Australian datasets the scores are almost always just
below those of model (2).
However, more substantial is the improvement in the fit of the Valencia Region
dataset, with scores almost 30% lower. As it can be seen in Figure 2, model (4)
outperforms model (2) in the accidental bump region, although it loses something
by underestimating death at older ages.
Figure 2 – Graduation of mortality data for the Valencia region (1999-2001) using model
(4) (solid line) and model (2) (broken line). The observed qx values are indicated by dots.
log(q x)
-7 -6 -5 -4 -3 -2 -1 0
0 20 40 60 80
The last model we propose takes the component of (4) and the
component of (3)
x