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Re: Using tfr2 to Calculate age specific marital fertility rate [message #18163 is a reply to message #18160] Wed, 02 October 2019 13:04 Go to previous messageGo to previous message
schoumaker is currently offline  schoumaker
Messages: 66
Registered: May 2013
Location: Belgium
Senior Member
Hello,

If I understand correctly what you want to do, you should use

. tabexp v025, rates mina(15) maxa(19)
weight variable is v005
Preparing table of events and exposure for 3 year(s) preceding the survey
Period covered: 8/2013 to 7/2016
Central date is 2015.0982
Number of cases (women): 2335
Number of person-years (weighted): 4482.1265
Number of events (weighted): 318.67191

v025 period ageg events exposure centry rate se_r
urban 0 15 178.119 2852.75 2015.098 .0624375 .0046783
rural 0 15 140.553 1629.376 2015.098 .086262 .0072761

You get the adolescent fertility rate in each place of residence, and you obtain the weighted exposure and weighted number of births.

You can check that the weighted mean of the rates (exposure used as weights) is equal to the rate at the country level : 2852,75*0,0624375+1629,376*0,086262=0,0710984


. tabexp, rates mina(15) maxa(19)
weight variable is v005
Preparing table of events and exposure for 3 year(s) preceding the survey
Period covered: 8/2013 to 7/2016
Central date is 2015.0982
Number of cases (women): 2335
Number of person-years (weighted): 4482.1265
Number of events (weighted): 318.67191

period ageg events exposure centry rate se_r
0 15 318.672 4482.126 2015.098 .0710984 .0039828


*******************

In contrast, if you do

tabexp if v025==1, rates
tabexp if v025==2, rates

or

by v025, sort: tabexp, rates

the rates will be the same, but weighted events and exposure will not be the same as in the previous example, because the weights are normalized so that their sum is equal to the sample size. So, doing it separately by place of residence will not allow you to estimate the share of exposure in each place of residence. If sampling weights were all equal to 1, the two approaches would lead to the same results.

Since you mentioned you tried also the following command, I will briefly comment on this.

. tabexp if v012 <=19 & v025 ==1

Here, you are not computing events and exposure beetween 15-19, but among women aged 15-19 at the time of the survey. By default, the minimum age in tabexp and tfr2 will be 15. So, three years before the survey, you will only get events and exposure among women 15-16. So, if you want to work on a specific age group, use minage and maxage options, but do not select people on the age at the time of the survey.

Best,

Bruno

Bruno Schoumaker
Centre for Demographic Research
Université catholique de Louvain

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