Click here to load reader

Demography CH3

  • View

  • Download

Embed Size (px)



Text of Demography CH3

  • DEMOGRAPHY III Statistics , AC 2014/15

    Demography CH 3 A.R.Muralidharan, Asst. Prof. in statistics WU Page 1

    DEMOGRAPHY3. Mortality3.1.Concepts and data requirements of death statistics3.2. Percentage distribution of death3.3.Basic Mortality measures

    3.3.1. Crude death rate3.3.2. Specific death rates3.3.3. Age specific death rates (ASDR)3.3.4. Graphical presentation of ASDR

    3.4.Standardization methods3.5.Conventional infant mortality rates3.6.Maternal death rate3.7.Life tables

    3.7.1. Types of life tables3.7.2. Life tables functions3.7.3. Construction of a simple life table3.7.4. Interpretation of a simple life table

    3.0. MortalityIn demography, mortality is related to Death. It is a principal Vital event for which vital statisticsare collected and complied by the vital statistics registration system (VRS). The purposes of deathstatistics in demography are

    1. Analysis of the present demographic status of the population as well as its potential growth2. Filling the administrative and research needs of public health agencies in connection with

    the development, operation and evaluation of public health programs3. Determination of administrative policy and action in connection with the programs of

    government agencies other than those concerned with public health4. Filling the need for information on population changes in relation to numerous professional

    and commercial activities;Death analysis are very much important in making analysis of past population changes which arerequired for making projections of population and other demographic characteristics

    3.1.Concepts and data requirements of death statisticsConcepts:It is necessary to gain knowledge about mortality. Mortality is one of the vital events.The UN and WHO have proposed the following definition of DeathDeath is the permanent disappearance of all evidence of life at any time after birth has takenplace.

  • DEMOGRAPHY III Statistics , AC 2014/15

    Demography CH 3 A.R.Muralidharan, Asst. Prof. in statistics WU Page 2

    A death can occur only after a live birth has occurred. This definition of death can be easilyunderstandable. The definition of a death excludes deaths prior to birth that is so-called fetaldeath. A fetal death is formally defined as Death prior to the complete expulsion or extractionfrom its mother of a product of conception irrespective of duration of pregnancy. The death isindicated by the fact that after such separation the fetus does not breathe or show any otherevidence of life such as beating of the heart, pulsation of the umbilical cord or definite movement ofvoluntary muscles. The term fetal dath is employed in present demographic practice to differencethe other deaths such as stillbirth, miscarriages, and abortions in popular, medical and legal usages.The term stillbirth is defined as a death that occurs in the duration of 20 or 28 weeks of gestation ormore. This term is employed in the place of late fetal deaths.The termMiscarriage is defined as spontaneous or accidental terminations of fetal life occurringearly in pregnancy.The term abortion is popularly used to refer to induced early fetal deaths, including both thosewhich are legal or illegal. In medical usage, an abortion is the expulsion of the fetus prematurely,particularly at any time be for it is visible or capable of sustaining life. From a technical point of viewthe terms abortion and miscarriage can be hard to distinguish.The recommendation of UN and WHO is to group all of these events : miscarriage and abortion aswell as still births under the heading of Fetal Death and to classify them as early, intermediate andlate according to the months of gestation.Data requirements of death statisticsThe basic data on deaths for mortality studies, for the statistically developed areas , come from vitalstatistics registration systems and less commonly, from national population register systems. Theanalysis of death statistics from the vital statistics registration depends on the availability ofappropriate population data from a census or survey or population estimates to be used as bases forcomputing rages of various kinds. This dependence on a second data collection is avoided where anadequate national population register system is in effect.The VRS is likely to be inadequate in the underdeveloped countries: for these areas, other sources ofdata for measuring morality have to be considered. The principle alternative sources are

    1. National census and2. National sample surveys.

    Census data and sample surveys may providea. Data on age composition on recent mortality andb. Direct data on mortality

  • DEMOGRAPHY III Statistics , AC 2014/15

    Demography CH 3 A.R.Muralidharan, Asst. Prof. in statistics WU Page 3

    3.2.Percentage distribution of deathA distribution of deaths by age is percentage distribution of death. It has a pattern based on thedeath data. It is described as in x-axis with age and in y- axis percentage of deaths in the givenregion or area or country.A combination of high rates and large proportion of children in the population as occurs in manyunder developed countries, results in a tremendous proportion of deaths among children under age5. On the other hand, in certain developed countries the proportion of deaths of young children isvery small.

    3.3.Basic Mortality measures3.3.1. Crude death rate (C.D.R)

    It is the simplest of all the indices of mortality. It is defined as the number of deaths per K personsin the population of any given region or community during a given period. Thus in particular theannual Crude death rate denoted by m for any given region or community is given by= where k = 1000 usuallyThe CRD for any period gives the rate at which the population is depleted through deaths over thecourse of the period.The midyear population is employed as an approximation to the average population exposed torisk of death during the year. The midyear population may approximated by combining data onbirths, deaths and immigration for the period between the census date and the estimated date withthe count from the last census, as an arithmetic or geometric mean of the population estimateddirectly on the basis of these components for two successive dates usually it will be January 1 and inother ways.Crude death rates may be computed for any period, but typically they are computed for the calendaryear or the Fiscal year. That is the 12 month period from July1 to June 30.In the latter case, the population figure should relate to January 1 of the fiscal year. Crude deathrates are calculated for 12 month periods such as calendar years or fiscal years so as to eliminate theeffect of seasonal or monthly variations on the comparability of the rates.Merits and demeritsMerits

    1. It is simple and easy to calculate2. CRD is perhaps the most widely used of any vital statistics rates3. By CDR is a probability that a person belonging to the given population will die in the given


  • DEMOGRAPHY III Statistics , AC 2014/15

    Demography CH 3 A.R.Muralidharan, Asst. Prof. in statistics WU Page 4

    Demerits1. It ignores the age and sex distribution of the population2. CDR is not suitable for comparing the mortality in two places.

    RemarkWe can compute the CDR for males and females separately.

    For male the formula: 1000 where mD is number of male deaths and mP is male population inthe given region during the given period. Similarly for female the formula is 1000CDR usually lies between 8 and 30 per thousand and female CDR is generally less than male CDR.

    3.3.2. Specific death ratesThe CDR gives only a very general indication of the level of mortality and its changes In other wordswhile computing CDR, there was a drawback that it ignores the age and sex of the population. Thereis also need for measures that describe the specific components of the overall number of deaths andthe crude rate. Various types of specific death rates are interest in the analysis. To overcome thisdrawback we must need a more useful figure than CDR, we must take into the fact that the mortalitypattern is different in different segments of the population. Various segments may be age, sex,occupation, etc.,Death rate computed for a particular specified section of the population is termed as specific deathrate (SDR). SDR for given geographical region during a given period is

    SDR =

    Usually SDR is computed specific to age and sex.3.3.3. Age specific death rates (ASDR)

    As we know age is the most important variable in the analysis of mortality. Most tabulation ofdeaths requires cross- classification with age if they are to be useful. The tabulations of deaths byage are subject to a number of deficiencies. The principal ones are substantial and variable under-registration of deaths by age, extensive misreporting of the age of the decedent, and an excessiveproportion of age not stated. Reporting of age decedents among the extreme aged is believed tobe quite inaccurate.The principle way of measuring the variation in mortality by age is in terms of age-specific deathrates.An ASDR is defined conventionally as the number of deaths of persons of a given age during a yearper1000 of the midyear population at the age.

    ASDR = 1000