Age-Specific Abortion Fate (ASAR): Based on Age-Period Rates.
Coverage:
Population base: Women age 15-49 years in seven five-year age groups (15-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49 years) (IR file)
Time period: Three years preceding the survey
Numerators: Number of induced abortions that occurred in a period (typically the 1-36 months before the survey) to women in the age group at the time of the induced abortion (v008 - p3 in 1:36 & p32 = 4) (GR file)
Denominator: Number of women-years of exposure in the same period (1-36 months before the survey) of women in the age group (IR file)
Variables: IR file.
|
p3 |
CMC date of end of pregnancy |
|
p32 |
Pregnancy outcome reclassified |
|
v011 |
CMC date of birth of respondent |
|
v008 |
CMC date of interview |
|
v005 |
Woman’s individual sample weight |
The age-specific abortion rate is calculated as the quotient of the numerator divided by the denominator for each age group, multiplied by 1000. The result is an average rate over the 36-month period, expressed as an annual rate per 1000 women.
Numerator: Induced abortions are tabulated according to period of the date of the induced abortion and the age of mother at the time of the date of the induced abortion:
Period of induced abortion: The period of the induced abortion is calculated as the difference in months between the date of interview and the date of the induced abortion, both in century-month code format (CMC). Induced abortions are included in the tabulation if they occur 1-36 months before the survey (v008 - p3 in 1:36).
Age of mother at the time of the induced abortion: The difference in months between the date of the induced abortion and the date of birth of the mother both in CMC. The difference is then divided by 60 and truncated to whole numbers to form the age groups (agegroup = int( (p3 - v011) /60) ). Note that age group 15-19 is classified as age group 3 here, not age group 1. Induced abortions are tabulated by age group.
Denominator: Women-years of exposure are calculated as the sum of the number of months exposed in the five-year age group during the time period divided by 12. A woman can contribute exposure to several age groups in the period, depending on the length of the period. For periods exceeding five years a woman can contribute to more than two age groups. For a period of three years or five years a woman will contribute to no more than two five-year age groups during the 36- or 59-month period. The description below assumes a period of 1-36 months preceding the survey, and that a woman contributes to at most two age groups, described here as the higher age group and the lower age group:
Higher age group: A woman’s age at the end of the period determines the higher age group. The higher age group is calculated by subtracting the women’s date of birth from the date of interview minus one (in CMC), dividing the difference by 60 and truncating to a whole number (agegroup = int( (v008-1-v011)/60 ). The -1 is to ignore the month of interview and use just the 36 months prior to but not including the month of interview.
The number of months spent in the higher age group is the difference in months between her age at the end of the period of exposure (date of interview less one month) and the lower age limit of the age group plus one month (exposure = v008 - 1 - v011 - agegroup*60 + 1). As the -1 and the +1 cancel out this can be simplified to (exposure = v008 - v011 - agegroup*60). If the number of months in the age group exceeds 36 then the exposure is truncated to 36 for the period (exposure = 36 if exposure > 36). If the number of months in the age group is less than the duration of the time period (36 months), then the woman contributes exposure to both the higher age group and the next lower age group (agegroup-1).
Lower age group: The contribution to the lower age group is 36 less the number of months of exposure in the higher age group. If the number of months in the higher age group is greater than the duration of the time period (i.e., >36 months), then the exposure in the higher group is the duration of the period (36 months) and the exposure in the lower age group is zero.
Tabulation: Each woman is tallied twice, once according to her higher age group accumulating the exposure she contributes to that group and once in the lower age group accumulating lower age group exposure. For ever-married samples, the exposure is adjusted to represent all women by multiplying the exposure by the woman’s “all women factor” (awfactt), which is derived from the proportion of women ever-married from the persons data file (PR file). See the section on All Women Factors for details on their calculation. The total exposure in each age group is then the sum of the exposure in each age group from the first and second tallying.
Example 1: A woman interviewed in September 2022, born in May 1991. Her CMC date of interview is 12*(2022 - 1900) + 9 = 1473. The CMC of the date of the end of the period of exposure is 1473 - 1 = 1472. Her CMC date of birth is 12*(1991 - 1900) + 5 = 1097. Her age in months at the end of the period is 1472 - 1097 = 375. The age group at the end of the period is 375/60 = 6.25, truncated to 6. This represents age group 30-34 years (30 = 6*5 years interval). The number of months in this age group is 375 - 6*60 + 1 = 16 months. Since this is less than the total number of months during the period (36 months), she contributed 16 months to age group 30-34 during the period and 36 - 16 = 20 months to the age group 25-29 during the period.
Example 2: A woman interviewed in September 2022, born in March 1998. Her CMC date of interview is 12*(2022 - 1900) + 9 = 1473. The date of the end of the period of exposure is 1473 - 1 = 1472. Her CMC date of birth is 12*(1998 - 1900) + 3 = 1179. Her age in months at the end of the period is 1472 - 1179 = 293. The age group at the end of the period is 293/60 = 4.88, truncated to 4. This represents age group 20-24 years (20 = 4*5 years interval). The number of months in this age group is 293 - 4*60 + 1 = 54 months. Since the number of months in this age group is greater than 36 months, she contributed 36 months of exposure to age group 20-24 during the period and no exposure to the next lower age group during the period.
The total number of pregnancies that a woman has had is recorded obligatorily by the interviewer; no unknown numbers of pregnancies are allowed. There are three values involved in the calculation of ASAR, interview date, birth date of woman and dates of induced abortions. The interview date is always known from fieldwork dates. If missing or unknown, the birth date of the interviewed women and the dates of the end of her pregnancies are imputed before formation of the standard recode file. See Date Variables in Chapter 1.
Induced abortions to women at ages less than 15 years or more than 49 years at the time of the abortion are not included in the calculation of these ASARs.
Induced abortions in the month of interview are excluded. This exclusion is because this month does not represent a full month but is censored by the date of interview.
A three-year (36 month) time period is taken for calculating current ASAR. This period is a compromise between the need for recency and reduction of sampling variation.
No adjustment is made for truncation by age. Women who are at most 49 years at the time of interview were 48 years the year before and 47 years two years before. The reason no adjustment is made is that the tiny probability of women age 48 and 49 years of age having an induced abortion in the three years preceding the survey outweighs the complication of adjusting by single years of age.
In line with general DHS policy, no adjustment is made for possible omission or date misreporting of the dates of induced abortions or misreporting of the date of birth of the woman.
For ever-married samples, it is assumed that never-married women have not had any induced abortions. Only the denominator of the rates is adjusted to estimate the number of all women exposed in the age group.
The calculation of the ASARs is completely analogous to the calculation of Age Specific Fertility Rates described earlier in this chapter.
These indicators were not typically reported prior in most surveys prior to DHS-8, but have been reported in some surveys prior to DHS-8 that included full pregnancy histories
Croft, T. 1991. “Date Editing and Imputation”. In Demographic and Health Surveys World Conference Proceedings, II: 1337-1356, Columbia, Maryland: IRD/ORC Macro. https://dhsprogram.com/publications/publication-DHSG3-DHS-Questionnaires-and-Manuals.cfm
Gilda Sedgh, Akinrinola Bankole, Susheela Singh, Michelle Eilers. 2013. Legal Abortion Levels and Trends By Woman's Age at Termination. Perspectives on Sexual and Reproductive Health, 45(1):13–22.
Westoff, Charles F. 2005. Recent trends in abortion and contraception in 12 countries. DHS Analytical Studies No. 8. Calverton, Maryland, USA: ORC Macro. http://dhsprogram.com/pubs/pdf/AS8/AS8.pdf.
DHS-8 Tabulation plan: Table 5.15
API Indicator IDs:
FE_ABRT_W_A15, FE_ABRT_W_A20, FE_ABRT_W_A25, FE_ABRT_W_A30,
FE_ABRT_W_A35, FE_ABRT_W_A40, FE_ABRT_W_A45
Age-Specific Abortion Rate (ASAR) for age group 10-14: Based on Age-Period Rates.
Coverage:
Population base: All girls age 10-14 years during the time period (IR file)
Time period: Three years preceding the survey
Numerator: Number of induced abortions that occurred in a period (typically the 1-36 months or 1-60 months before the survey) to girls in the age group 10-14 at the time of the induced abortion (v008 - p3 in 1:36 [or 60] & p32 = 4) (GR file)
Denominator: Number of years of exposure in the same period of girls in the age group 10-14 (IR file)
Variables: GR file, IR file.
|
p3 |
CMC date of end of pregnancy |
|
p32 |
Pregnancy outcome reclassified |
|
v011 |
CMC date of birth of respondent |
|
v008 |
CMC date of interview |
|
v005 |
Woman’s individual sample weight |
|
awfactt |
All women factor (only needed with ever-married samples) |
The ASAR 10-14 is calculated as the quotient of the numerator divided by the denominator for each age group, multiplied by 1000. The result is an average rate over the 36- or 59-month period, expressed as an annual rate per 1000 women. The age-specific abortion rate for age group 10-14 is calculated in a similar manner to the ASARs for age groups between 15 and 49, but with adjustments to both numerator and denominator to avoid biases as girls age 10-14 are not typically interviewed in DHS surveys, and the ASAR 10-14 is based on retrospective data for women age 15-19.
Numerator: Induced abortions are tabulated according to period of the induced abortion and the age of mother at the time of the induced abortion, and are adjusted for truncation of reports:
Period of induced abortion: The period of the induced abortion is calculated as the difference in months between the date of interview and the date of the induced abortion, both in century-month code format (CMC). Induced abortions are included in the tabulation if they occur 1-36 months before the survey (v008 - p3 in 1:36 [or 60] & p32 = 4).
Age of mother at the time of the induced abortion: The difference in months between the date of the induced abortion and the date of birth of the mother both in CMC. The difference is then divided by 12 and truncated to whole numbers to form single year age groups (singleage = int( (p3 - v011) /12 ). Induced abortions are tabulated by single year age group for ages 10-14. Note that the use of single year age groups is different than the five-year age groups used for ASARs for ages 15 to 49.
Adjustment of number of induced abortions due to truncation of reports: The adjustment for the ASAR 10-14 is exactly the same as the adjustment used for the Age Specific Fertility Rate 10-14 (see Figure 5.1 above). This figure shows the reports available for the calculation of ASAR 10-14 (in blue) and the data not available due to truncation (in red) for both a three-year period and a five-year period immediately preceding the survey. For a three-year (36-month) period, for age 14 data are reported for 5/6 of the induced abortions and exposure, for age 13 for 3/6, and for age 12 for 1/6. For ages 11 and 10 no data are reported. The induced abortions for ages 12-14 are thus adjusted by the inverse of these proportions – 6/5 for age 14, 6/3 for age 13, and 6/1 for age 12. For ages 11 and 10, the assumption is that there are no induced abortions in these age groups. For a five-year (60-month) period similar adjustments of 10/9, 10/7, 10/5, 10/3, 10/1 are made for ages 14, 13, 12, 11, and 10 respectively. After adjusting the number of induced abortions, the total induced abortions in each single age is summed to produce an aggregate for the age group 10-14.
Denominator: Person-years of exposure are calculated as the sum of the number of months exposed in each single-year age group for ages 10-14 during the time period, adjusted for truncation of reports (see below), divided by 12. A girl can contribute exposure to several single year ages in the period, depending on the length of the period, and may contribute to x+1 single year ages for a period covering x years.
Oldest age: A girl’s age at the end of the period determines the oldest age. The oldest age is calculated by subtracting the girl’s date of birth from the date of interview minus one (in CMC), dividing the difference by 12 and truncating to a whole number (singleage = int( (v008-1-v011)/12 ). The -1 is to ignore the month of interview and use just the 36 (or 60) months prior to but not including the month of interview.
The number of months spent in the oldest age is the difference in months between her age in months at the end of the period of exposure (date of interview less one month) and the lower age limit in months of the age group plus one month (exposure = v008 - 1 - v011 - singleage*12 + 1). As the -1 and the +1 cancel out this can be simplified to (exposure = v008 - v011 - singleage*12). The remaining exposure (to be covered by other ages) is 36 or 60 minus the exposure.
Other ages: Starting one year before the oldest age, the contribution of exposure to other ages is the minimum of either 12 months or the remaining exposure in months. After tallying the exposure for a single year age, the remaining exposure is reduced by the amount contributed, the single year age is reduced by one year and the tallying repeated for the next lower age until the remaining exposure is 0 or the age is outside of 10-14.
Tabulation: Each girl is tallied once per single year age for each age she was exposed for in the period, accumulating the exposure she contributes to that age. For ever-married samples, the exposure is adjusted to represent all girls by multiplying the exposure by the “all women factor” (awfactt), which is derived from the proportion of women ever-married from the persons data file (PR file). See the section on All Women Factors for details on their calculation in Chapter 1. The total exposure in the age group 10-14 is then the sum of the exposure in each single age adjusted for truncation of reports (see below).
Adjustment of years of exposure due to truncation of reports: As for the induced abortions, similar adjustments are made for the exposure. For a 36-month period the exposure for ages 12-14 are thus adjusted by the inverse of these proportions – 6/5 for age 14, 6/3 for age 13, and 6/1 for age 12. After adjusting the exposure, the total exposure in each single age is summed to produce an aggregate for the age group 12-14. As no exposure is collected for ages 11 and 10, the assumption is that the exposure per single year age for ages 10 and 11 is the same as the average for ages 12-14, and so the exposure is multiplied by 5/3 to produce an estimate of exposure for ages 10-14. For a 60-month period, similar adjustments of 10/9, 10/7, 10/5, 10/3, 10/1 are made to the single year exposure for ages 14, 13, 12, 11, and 10 respectively before summing the total exposure for ages 10-14.
Example 1: A woman interviewed in September 2022, born in June 2007. Her CMC date of interview is 12*(2022 - 1900) + 9 = 1473. The date of the end of the period of exposure is 1473 - 1 = 1472. Her CMC date of birth is 12*(2007 - 1900) + 6 = 1290. Her age in months at the end of the period is 1472 - 1290 = 182. The single age group at the end of the period is 182/12 = 15.17, truncated to 15. The number of months in this age group is 182 - 15*12 + 1 = 3 months. For the oldest age group (15) she would contribute 3 months, however, age 15 is outside the age group range of 10-14, so no tallying is done for this age group. The remaining exposure in the 36-month period would be 36 – 3 = 33 months. For the next age younger group (14) she contributes the minimum of the remaining exposure (33 months) or 12 months, so thus contributes 12 months and the remaining exposure becomes 21 months. For age 13 she again contributes 12 months, and the remaining exposure becomes 9 months. For age 12 she contributes just the remaining exposure (9 months) to this age in the period.
Summary of exposure for example 1:
|
Age |
Exposure |
Remaining exposure |
Tallying |
|
15 |
3 |
33 |
No tallying as too old |
|
14 |
12 |
21 |
12 months at age 14 |
|
13 |
12 |
9 |
12 months at age 13 |
|
12 |
9 |
0 |
9 months at age 12 |
Example of adjustments for induced abortions and exposure for three-year period:
|
Age |
Abortions |
Exposure |
Adjustment |
Abortions adjusted |
Exposure adjusted |
|
12 |
1 |
450 |
6/1 |
6 |
2700 |
|
13 |
4 |
1500 |
6/3 |
8 |
3000 |
|
14 |
10 |
2500 |
6/5 |
12 |
3000 |
|
Sum for 12-14 |
|
|
|
26 |
8700 |
|
Sum for 10-14 |
|
|
5/3 for exposure only |
26 |
14500 |
|
ASAR 10-14 |
|
Abortions/ |
Exposure |
= |
.0018 |
The total number of pregnancies a woman has had is recorded obligatorily by the interviewer; no unknown numbers of induced abortions are allowed. There are three values involved in the calculation of ASAR, interview date, birth date of woman and dates of induced abortions. The interview date is always known from fieldwork dates. If missing or unknown, the birth dates of interviewed women and the dates of her induced abortions are imputed before formation of the standard recode file. See Date Variables in Chapter 1.
The ASAR 10-14 is typically calculated for the three years that precede the date of the survey and is presented as an annual rate.
Induced abortions to women while age 15 or higher are not included in the calculation of the ASAR 10-14, however, induced abortions to girls age 10-14 at the time of the induced abortion are included in the calculation of the ASAR 10-14.
Induced abortions in the month of interview are excluded. This exclusion is because this month does not represent a full month but is censored by the date of interview.
In line with general DHS policy, no adjustment is made for possible omission or date misreporting of the dates of induced abortions or misreporting of the date of birth of the woman.
For ever-married samples, it is assumed that never-married women have not had any induced abortions. Only the denominator of the rates is adjusted to estimate the number of all women exposed in the age group.
See References for Age-Specific Abortion Rates (ASAR).
DHS-8 Tabulation plan: Table 5.15
API Indicator ID:
FE_ABRT_W_A10
The total abortion rate (TAR) is an age-period abortion rate for a synthetic cohort of women. It measures the average number of induced abortions a group of women would have by the time they reach age 50 if they were to have induced abortions at the current age-specific abortion rates. The TAR is expressed as the average number of induced abortions per woman. Unless otherwise specified, the TAR is for all women.
Coverage:
Population base: Women age 15-49 (IR file)
Time period: Three years preceding the survey, excluding the month of interview (1-36 months before the survey)
The TAR is the sum of the Age-Specific Fertility Rate (ASFR) for all women multiplied by five. The ASARs are those for the seven five-year age groups from 15-19 to 45-49.
See Handling of Missing Values for Age-Specific Abortion Rates (ASAR).
The TAR is presented only for women age 15-49 and does not include abortions outside the age range of 15-49 years.
See References for Age-Specific Abortion Rates (ASAR).
DHS-8 Tabulation plan: Table 5.15
API Indicator ID:
FE_ABRT_W_TAR
The general abortion rate (GAR) is the average number of induced abortions currently occurring to women of reproductive age in the period, typically 1-36 months preceding the survey, expressed per 1,000 women age 15-44.
Coverage:
Population base: All women 15-44 years of age during the period (IR file)
Time period: Three years preceding the survey excluding the month of interview (1-36 months)
Numerator: Total number of induced abortions in the period (v008 - p3 in 1:36 & p32 = 4) (GR file)
Denominator: Total number of women-years of exposure during period (IR file)
Variables: GR file, IR file.
|
p3 |
CMC date of end of pregnancy |
|
p32 |
Pregnancy outcome reclassified |
|
v011 |
CMC date of birth of respondent |
|
v008 |
CMC date of interview |
|
v005 |
Woman’s individual sample weight |
|
awfactt |
All women factor (only needed with ever-married samples) |
Numerator: The total of all induced abortions in the period to all women age 15-49, irrespective of their age at the time of the abortion (v008 - p3 in 1:36).
Denominator: The sum of the women-years of exposure over the five-year age groups from 15-19 to 40-44 tabulated as for the age-specific fertility rates.
GAR is the numerator divided by the denominator, multiplied by 1000.
See Handling of Missing Values for Age-Specific Abortion Rates (ASAR).
All induced abortions in the period are counted including induced abortions to women age 45-49 and induced abortions to women before they reached age 15. The exposure is limited to women age 15-44 and does not count the exposure for women age 45-49 in the denominator.
For ever-married samples, all women factors are applied in the tabulation of the denominators, as for the age-specific fertility rates.
See References for Age-Specific Abortion Rates (ASAR).
DHS-8 Tabulation plan: Table 5.15
API Indicator ID:
FE_ABRT_W_GAR