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Calculate Total Fertility Rates

Source: R/tfr.R
tfr.Rd

Calculate the total fertility rate (TFR) from age-specific fertility rates.

Usage

tfr(
  data,
  asfr = NULL,
  age = age,
  sex = NULL,
  by = NULL,
  denominator = 1,
  suffix = NULL
)

Arguments

data

Data frame with age-specific fertility rates and age

asfr

Age-specific fertility rates. Possibly an rvec.

age

<tidyselect> Age group labels. The labels must be interpretable by functions such as reformat_age() and age_group_type(). The age groups must not have gaps, and the highest age group must be "closed" (ie have an upper limit.)

sex

<tidyselect> Sex/gender of the child (not the parent).

by

<tidyselect> Separate total fertility rates are calculated for each combination the by variables. If data is a grouped data frame, then the grouping variables take precedence over by.

denominator

The denominator used to calculate asfr. Default is 1.

suffix

Optional suffix added to "tfr" column in result.

Value

A tibble.

Details

The total fertility rate is a summary measures for current fertility levels that removes the effect of age structure. Is obtained by summing up age-specific fertility rates, multiplying each rate by the width of the corresponding age group. For instance, the rate for age group "15-19" is multiplied by 5, and the rate for age group "15" is multiplied by 1.

The total fertility rate can be interpreted as the number of average children that a person would have, under prevailing fertility rates, if the person survived to the maximum age of reproduction. The hypothetical person is normally a woman, since age-specific fertility rates normally use person-years lived by women as the denominator. But it can apply to men, if the age-specific fertility rates are "paternity rates", ie rates that use person-years lived by men as the denominator.

Sex-specific fertility rates

Age-specific fertility rates do not normally specify the sex of the children who are born. In cases where they do, however, rates have to be summed across sexes to give the total fertility rates. If tfr() is supplied with a sex argument, it assumes that sex applies to the births, and sums over the sexes.

Denominator

Published tables of age-specific fertility rates often express the rates as births per 1000 person-years lived, rather than per person-year lived. (Sometimes this is expressed as "births per 1000 women".) In these cases

Using rvecs to represent uncertainty

An rvec is a 'random vector', holding multiple draws from a distribution. Using an rvec for the asfr argument to tfr() is a way of representing uncertainty. This uncertainty is propagated through to the TFR, which will also be rvecs.

See also

  • lifeexp() Calculate life expectancy from age-specific mortality rates.

Examples

iran_fertility |>
  tfr(asfr = rate,
      by = c(area, time),
      denominator = 1000)
#> # A tibble: 30 × 3
#>    area   time   tfr
#>    <chr> <dbl> <dbl>
#>  1 Rural  1986  7.08
#>  2 Rural  1987  6.87
#>  3 Rural  1988  6.62
#>  4 Rural  1989  6.55
#>  5 Rural  1990  6.43
#>  6 Rural  1991  6.01
#>  7 Rural  1992  5.29
#>  8 Rural  1993  4.90
#>  9 Rural  1994  4.37
#> 10 Rural  1995  3.82
#> # ℹ 20 more rows