Median Age at Any Event [message #29806] |
Wed, 07 August 2024 12:40 |
crabyou
Messages: 1 Registered: August 2024
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Member |
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Since I had to spend a day to finally figure out how the median age variables on NFHS reports are calculated, here is the code for anyone trying the same. I do not claim originality, I have taken snippets of code from multiple sources to customise this code. I illustrate the code below with NFHS-5 data and reports.
program define calc_median_age
** Source: https://userforum.dhsprogram.com/index.php?t=msg&goto=12912&&srch=svyset+individual+data#msg_12912
replace age=99 if age==. | age==0 // age is any age var of interest. ideally these should be coded missing but the values in NFHS reports will differ slightly without this recoding
summarize age [fweight=v005], detail
scalar sp50=r(p50)
gen dummy=0
replace dummy=1 if age<sp50
summarize dummy [fweight=v005]
scalar sL=r(mean)
replace dummy=0
replace dummy=1 if age<=sp50
summarize dummy [fweight=v005]
scalar sU=r(mean)
drop dummy
scalar smedian=round(sp50+(.5-sL)/(sU-sL),.01)
scalar list sp50 sL sU smedian
* warning if sL and sU are miscalculated
if sL>.5 | sU<.5 {
display in red "ERROR IN CALCULATION OF L AND/OR U"
}
drop age
end
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* EXECUTION BEGINS HERE
* sp50 is the integer-valued median produced by summarize, detail;
* what we need is an interpolated or fractional value of the median.
* In the program, "age" is reset as age at first any event of interest.
* sL and sU are the cumulative values of the distribution that straddle the integer-valued median
set maxvar 10000
use "NFHS/IAIR7EDT/IAIR7EFL.DTA", clear // individual level women data
************************* Create Variables ***********************************
**** Age at first marriage
replace s308c=. if s308c==9998 | s308c==9997 // inconsistent ( coded as 9997 ) or don't know ( coded as 9998 )
replace s309=. if s309==98 // dont know is coded as 98
**Source: suggested method for calculating age at marriage https://userforum.dhsprogram.com/index.php?t=msg&goto=14267&S=Google#:~:text=Can%20anyone%20illustrate%20this%20variable%3F&text=*Using%20this%20syntax%2C%20it%20has,before%2018%20years%20of%20age.
gen afm= int((s308c - v011) / 12)
replace afm=s309 if afm==.
la var afm "Age at First Marriage"
**** Age at first birth
gen afb= int((v211-v011)/12)
la var afb "Age at First Birth"
************************** Replicate Numbers on Report *************************
****** Source: https://dhsprogram.com/pubs/pdf/FR375/FR375.pdf
***** Median age at first marriage is 19.2 years among women age 20-49 - Page 208
preserve
gen age=afm
keep if v013!=1 // 20-49 olds
calc_median_age
scalar median_ans=smedian
scalar list median_ans
restore
***** Median age at first birth among women age 25-49 in India is 21.2 years - Page 114
preserve
gen age=afb
keep if v013!=1 & v013!=2 // 25-49 olds
calc_median_age
scalar median_ans=smedian
scalar list median_ans
restore
For calculating median age at any event for men, replace the weights (v005) with men's sample weights. I have also added the relevant links I had referred to.
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Re: Median Age at Any Event [message #29809 is a reply to message #29806] |
Wed, 07 August 2024 14:01 |
Bridgette-DHS
Messages: 3190 Registered: February 2013
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Senior Member |
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Following is a response from Senior DHS staff member, Tom Pullum:
Glad you were able to locate this simple procedure. I wrote it several years ago and it is now included (with some variations) in the GitHub code wherever medians are required.
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