| 1. |
- Bengtsson, Tommy, et al.
(författare)
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Introduction
- 2019
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Ingår i: Demographic Research Monographs. - Cham : Springer International Publishing. - 2197-9286 .- 1613-5520. - 9783030050740 - 9783030050757 ; , s. 1-19
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Bokkapitel (refereegranskat)abstract
- Globally, the twenty-first century will witness rapid population ageing. Already in 2050, one out of five persons in the world, and one out of three in Europe, is expected to be 60 or over (UN 2015). Moreover, we have entered into a new stage of population ageing in terms of its causes, which have altered its consequences. In the first stage, lasting until the middle of the twentieth century in developed countries, population ageing was entirely due to the decline in fertility, with Sweden being commonly used as an example (Coale 1957; Bengtsson and Scott 2010; Lee and Zhou 2017). During this stage, the increase in life expectancy was primarily driven by declines in infant and child mortality. It worked in the opposite direction to the fertility decline, making the population younger since it added more years before, than after retirement (Coale 1957; Lee 1994). In the second stage of population ageing, which is the current situation, population ageing is primarily driven by the increase in life expectancy, which is now due to declining old-age mortality. As a result, more years are added after retirement than in working ages (Lee 1994). Could immigration or an upswing in fertility stop population ageing? The short answer is most likely not. The effect of migration on population aging is generally regarded as minor (Murphy 2017), and since population ageing is a global phenomenon, it will be of no general help anyway. A rapid increase in fertility is improbable and, in any case, an increase would take some 25 years before adding to the labor force. Instead, attention has been focused on how to adapt our social systems to the increasing number of elderly per worker – more so since the increase in the elderly-per-worker ratio came in parallel with a rise in per capita costs for the institutional care, home care, and general health care for the elderly.
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| 2. |
- Jones, Owen R., et al.
(författare)
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Diversity of ageing across the tree of life
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 505:7482, s. 169-
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Tidskriftsartikel (refereegranskat)abstract
- Evolution drives, and is driven by, demography. A genotype moulds its phenotype's age patterns of mortality and fertility in an environment; these two patterns in turn determine the genotype's fitness in that environment. Hence, to understand the evolution of ageing, age patterns of mortality and reproduction need to be compared for species across the tree of life. However, few studies have done so and only for a limited range of taxa. Here we contrast standardized patterns over age for 11 mammals, 12 other vertebrates, 10 invertebrates, 12 vascular plants and a green alga. Although it has been predicted that evolution should inevitably lead to increasing mortality and declining fertility with age after maturity, there is great variation among these species, including increasing, constant, decreasing, humped and bowed trajectories for both long-and short-lived species. This diversity challenges theoreticians to develop broader perspectives on the evolution of ageing and empiricists to study the demography of more species.
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