منابع مشابه
How many old people have ever lived?
BACKGROUND Uninformed generalizations about how many elderly people have ever lived, based on a poor understanding of demography, are found in a surprising number of important publications. OBJECTIVE We extend the methodology applied to the controversial question “how many people have ever been born?” initiated by Fucks, Winkler, and Keyfitz, to the proportion of people who have ever reached a ...
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This article surveys current answers to the factual question posed in the title and reviews the kinds of information that are needed to make these answers more precise. Various factors affecting diversity are also reviewed. These include the structure of food webs, the relative abundance of species, the number of species and of individuals in different categories of body size, along with other ...
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We suggest an updated estimate of the number of Esperanto speakers worldwide, based on the number of people in Facebook who indicate that they speak the language. A simple calculation accompanied by reasonable refinements leads to a number of approximately two million Esperanto users within the internet community alone, probably significantly more worldwide.
متن کاملHow many species have mass M?
Within large taxonomic assemblages, the number of species with adult body mass M is characterized by a broad but asymmetric distribution, with the largest mass being orders of magnitude larger than the typical mass. This canonical shape can be explained by cladogenetic diffusion that is bounded below by a hard limit on viable species mass and above by extinction risks that increase weakly with ...
متن کاملPerspective. How many women have osteoporosis?
Osteoporosis is widely viewed as a major public health concern, but the exact magnitude of the problem is uncertain and likely to depend on how the condition is defined. Noninvasive bone mineral measurements can be used to define a state of heightened fracture risk (osteopenia), or the ultimate clinical manifestation of fracture can be assessed (established osteoporosis). If bone mineral measur...
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ژورنال
عنوان ژورنال: Demography
سال: 1966
ISSN: 0070-3370,1533-7790
DOI: 10.2307/2060184