rectangularisation

CONT: La baisse de la mortalité aux âges jeunes fait que la courbe des survivants devient de plus en plus horizontale à ces âges jeunes et de plus en plus verticale aux âges avancés. À cette «rectangularisation», correspond la transformation de la «pyramide» des âges en une tour plus «cylindrique».

CONT: Related to the concept of an ""ultimate"" limit to length of life is the idea of compression of mortality. This term is invoked (e.g., Fries, 1980) to describe a population in which the proportion of people surviving to advanced ages begins to approach what is assumed to be a biologically (presumably genetic) predetermined age limit to human survival. At this limit, the survival curve ""rectangularizes"", although a mathematically precise formulation of what constitutes rectangularization is not yet available. There are, however, a general set of order relations for different types of ""survival curves"" that we can use graphically to illustrate rectangularization.