Revision as of 04:24, 3 February 2010

One of the first stages of analysis (132-1) consists of relating the population totals or number of events to other totals or numbers. The resulting indices are given various names. A ratio ^6★, also used for various purposes, is the quotient obtained by dividing quantities of the same kind. When the dividend and divisor belong to the same kind but different categories (men and women, children and women, different age-groups, for example) an other terminology might be used in non English languages, relating both quantities with a specific ratio ¹ (like a sex ratio). A proportion ² is a ratio which indicates the relation in magnitude of a part to the whole. A percentage ³ is a proportion expressed per hundred. A rate ⁴ is a special type of ratio used to indicate the relative frequency ⁵ of the occurrence of a particular event within a population or a sub-population in a specified period of time, usually one year. Although this usage is recommended, the term has steadily acquired a wider meaning and is often incorrectly used as a synonym for ratio (e.g. labor force participation rate, which is actually a proportion).

• 2. Proportion, n. - proportional, adj.
• 4. Rates are generally given per thousand, and where the term "rate" is used without additional qualification "per thousand" is generally understood. Some rates, however, are given per ten thousand, per one hundred thousand, or per million e.g. cause-specific death rates (421-10). On other occasions rates may be given per person or per hundred. The word "rate" is sometimes omitted, thus one may find the expression "a mortality of ten per thousand," but this is not recommended.
• 6. The total fertility rate (cf 639-4) is the sum of age-specific fertility rates (cf 633-9) over the age reproductive period and thus lost its inverse temporal dimension (per year). The difference is as important as between length and surface or velocity and acceleration. The term synthetic index (cf 132-5) is preferred in some languages to avoid the confusion with the inverse temporal dimension (per year) of a rate: number of demographic events divided by the time exposure or person-years. If used, the term rate in the expression total fertility rate refers to the implicit per woman, which is not enough to qualify as a rate but enough for a dimensionless ratio.

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