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The sex structure1 or sex distribution1 of the population is generally measured by the ratio of the total number of one sex2 to the total number of the population, or to the total number of the other sex. When the male sex is considered, we often speak of the masculinity3 of the population. The masculinity proportion4 is the proportion of males in the total population. The sex ratio5 is the ratio of the number of one sex to that of the other; the ratio of the number of men to the number of women is called the masculinity ratio5.
- 2. sex n. — sexual adj.
- 3. masculinity n. — masculine adj.
The terms males1 and females2 are commonly used in demography in place of men1 and women2 to refer to persons of each sex at all ages including boys3 and girls4, The word man5 is, however, also used in the sense of human being5.
Age1 is another fundamental characteristic of population structure (144-4). Generally it is expressed in years, or years and months, save in the case of very small children, where it may be given in months and days only, or in years and decimal fractions of years. Statisticians often round off the age to the number of complete years2 lived, and this is called age at last birthday3. Where the fraction of the last complete year lived is counted as a whole year, as in some actuarial applications, we speak of age next birthday4. Occasionally age at nearest birthday5 is given, where the age is rounded to the nearest integer. The term exact age6 is used, particularly in life table calculations, to denote the date when an individual reaches his birthday. Thus, a man will reach exact age 25 on his 25th birthday, and a man aged 25 will be between exact age 25 and exact age 26.
In demography, certain terms which have been taken from everyday language are used to denote different age periods1, though without precision. At the beginning of life comes childhood2. In general a child3 is a person who has not yet attained puberty (620-2). In the very early days of life, the child is called new-born4. A child at the breast5 is a child who has not yet been weaned from its mother. The term infant6 or baby6 may be used to denote a child who has not reached his first birthday, though in colloquial language it may be applied to slightly older children. Children who have not yet reached the compulsory school age are called pre-school children7, a school child8 is a child who habitually attends school.
- 6. infant n. — infancy n., the period of being an infant —. infantile adj. In legal terminology, an infant is a person who has not yet attained his majority, generally a person under 21 years of age, who is often called a minor.
Childhood is followed by adolescence1 which is marked by puberty (620-2). An adolescent2 is a person, who is entering adolescence. The terms young persons3 or juveniles3 are employed for men and women approaching adult age4. Those who have reached maturity4 are called adults5. Old age6 is frequently taken as beginning at the age at retirement7 (361-3) i.e., about 60 or 65 years. Persons above that age are called old people8.
- 3. The term youth is employed for a male young person, and also for the age period referred to.
- 4. maturity n. - mature adj. - maturation n.,the process of growing to maturity.
The age distribution of a population is either given by individual years of age1 or by age groups2, which may be quinquennial age groups3 or quinary age groups3, or broad age groups4, such as 0-19 years, 20-59 years, 60 years and over. Occasionally a population’s age distribution6 or age structure6 is given by classifying the population by year of birth5. Graphically an age distribution may be represented by a population pyramid7 which is a histogram (155-8) showing the population by age and sex and so named because of its pyramidal shape.
The mean age1 of a population is the average age of all its members, the median age2 is the age which divides it into two numerically equal groups. When the proportion of old people in a population increases, we speak of the ageing3 of the population. An increase in the proportion of young people may be called rejuvenation4 of the population. The term ageing used above should not be confused with the technique of ageing5 a population. This technique consists of applying certain ageing factors6 to particular age groups of the population, in order to compute the total number of survivors of that age group at a later date.
Ageing (326-5) of a population must also be distinguished from individual ageing1 or senescence1, and from an increase in the duration of human life or increased longevity2 which is the result of improved standards oi living and of medical discoveries. An individual’s physiological age3 will depend on the state of his tissues and organs. In the case of children we speak of mental age4, which is defined as the age at which the attainments of the individual child as measured by certain tests can be performed by the average child. In studies of mental and physiological age, a distinction is made between these ages and chronological age measured by the time elapsed since the individual’s date of birth5. The ratio of mental to chronological age is called the intelligence quotient6 (often abbreviated to I.Q.).
- 1. senescence n. — senescent adj.
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