Using IPUMS DHS Calendar Data to Create Event Files
IPUMS DHS allows users to download customized data files where the unit of analysis is a month in the contraceptive calendar. Sometimes users may wish to treat an event (such as a birth or spell of contraceptive use) as the unit of analysis. For example, this event-focused approach is helpful for life table analysis and for studying such topics as length of adherence to specific contraceptive methods and the timing and rate of contraceptive failure.
With events as the unit of analysis, each row in the data represents a reproductive event through the duration of the calendar.
After converting from the women-months to the women-events format, the event file will contain the following variables:
- 1. calcmc_ev_start
- CMC start of the event
- 2. calcmc_ev_end
- CMC end of the event
- 3. calreprod_allevents
- Numeric recode of reproductive event
- 4. ev_dur_months
- Duration of event in months
- 5. calreprod_prev_ev
- Prior reproductive event
- 6. prev_ev_dur
- Duration of prior event in months
- 7. calreprod_next_ev
- Next reproductive event
- 8. next_ev_dur
- Duration of next event in months
(Note: The full range of IPUMS DHS variables is also available and is unaffected by this conversion. Users may select as many or as few variables as they desire).
Table 1 provides a snapshot of how cases would look after converting from the woman-months to the woman-events format. Events are ordered from most recent to the earliest event recorded in the calendar data.
| calcaseid_cmc | calcmc_ev_start | calcmc_ev_end | calreprod_allevents | ev_dur | calreprod_prev_ev | prev_ev_dur | calreprod_next_ev | next_ev_dur |
|---|---|---|---|---|---|---|---|---|
| 12816 1_1402 | 1402 | 1402 | pregnanc | 1 | no contraceptive use | 13 | ||
| 12816 1_1389 | 1377 | 1389 | no contr | 13 | injection | 24 | pregnancy | 1 |
| 12816 1_1365 | 1342 | 1365 | injectio | 24 | no contraceptive use | 9 | no contraceptive use | 13 |
| 12816 1_1356 | 1348 | 1356 | no contr | 9 | birth | 1 | injection | 24 |
| 12816 1_1355 | 1355 | 1355 | birth | 1 | pregnancy | 8 | no contraceptive use | 9 |
| 12816 1_1347 | 1340 | 1347 | pregnanc | 8 | no contraceptive use | 8 | birth | 1 |
| 12816 1_1339 | 1332 | 1339 | no contr | 8 | birth | 1 | pregnancy | 8 |
| 12816 1_1338 | 1338 | 1338 | birth | 1 | pregnancy | 5 | no contraceptive use | 8 |
| 12816 1_1333 | 1329 | 1333 | pregnanc | 5 | birth | 1 | ||
| 18691 1_1389 | 1376 | 1389 | no contr | 14 | birth | 1 | ||
| 18691 1_1388 | 1388 | 1388 | birth | 1 | pregnancy | 8 | no contraceptive use | 14 |
| 18691 1_1380 | 1373 | 1380 | pregnanc | 8 | no contraceptive use | 24 | birth | 1 |
| 18691 1_1356 | 1333 | 1356 | no contr | 24 | withdrawal | 6 | pregnancy | 8 |
| 18691 1_1350 | 1345 | 1350 | withdraw | 6 | no contraceptive use | 4 | no contraceptive use | 24 |
| 18691 1_1346 | 1343 | 1346 | no contr | 4 | birth | 1 | withdrawal | 6 |
| 18691 1_1345 | 1345 | 1345 | birth | 1 | pregnancy | 8 | no contraceptive use | 4 |
| 18691 1_1337 | 1330 | 1337 | pregnanc | 8 | no contraceptive use | 4 | birth | 1 |
| 18691 1_1333 | 1330 | 1333 | no contr | 4 | pregnancy | 8 |
The approach suggested in Module 5 of the DHS Calendar Tutorial uses the collapse command in Stata to combine separate records for consecutive months into a single record representing an event. However, to facilitate easy use of multiple variables, IPUMS DHS proposes a different approach to reach the same end.
The general logic of converting the woman-months into events is as follows: 1) Counting total number of events. 2) Counting total number of months for each event. 3) A simple by sort keep, to preserve only one record per event. 4) Gain information about the former and the next event. 5) Generate CMC (century month codes) for start and end of event.
Step 1. Make a data file
- Log into the IPUMS DHS website using your approved DHS Program user name and password.
- Download a sample of your choice from the IPUMS DHS website (at dhs.ipums.org), using woman-months as the unit of analysis. (For this example, we picked Burundi 2016). Use the SEARCH function to find the following variables and select these variables for your data file:
- CALREPROD_ALLEVENTS (Numeric code of reproductive events for woman-month)
- INTDATECMC (Century month date of interview)
- The IPUMS DHS variable CALCMC_MONTH will also be used, but that variable is automatically preselected for inclusion in a data file with calendar data.
Step 2. Open the data file.
- Either change to a working directory where the data are stored or add the full path to the 'use' command below
-
cd "C:\data\IPUMS_DHS" - Open the dataset for use
-
use "idhs_00001.dta", clear
Step 3. Prepare the data for use.
- As IPUMS DHS has already done much of the heavy lifting, there is no need to destring the calendar information and to restructure the data (so you can skip Steps 7, 7.1, 7.2, and 7.3 of this example in the DHS Contraceptive Calendar Tutorial).
- To preserve the original order of the observations and generally prepare the data
-
gen long order=_n destring calid, replace destring calcmc_month, replace
Step 4. Count the number of events
- For example, if use of the Pill was interrupted by pregnancy and Pill use resumed after birth:
- Pill use prior to pregnancy is event 1
- Pregnancy is event 2
- Birth is event 3
- Resumption of pill use is event 4
- Stata code
-
generate new_ev=0 bysort sample calid (calcmc_month): replace new_ev=1 if calreprod_allevents[_n]!=calreprod_allevents[_n-1] bysort sample calid (calcmc_month): replace new_ev = 0 if _n==1 bysort sample calid (calcmc_month): gen ev_number = sum(new_ev)+1 bysort sample calid (calcmc_month): egen tot_ev = max(ev_number) - Count total number of months for each event
-
bysort sample calid ev_number (calcmc_month): gen ev_dur=_N
Step 5. Keep the last observation per event for each woman
- The DHS Contraceptive Calendar Tutorial suggests using the Stata command collapse. However, with the way IPUMS DHS data are organized, a simple bysort keep is more effective. In this way, only the last observation per event for each woman is retained.
-
bysort sample calid ev_number: keep if _n==_N
Step 6. Capture information about the previous and following events
- Capture the previous event and its duration
-
by sample calid: gen calreprod_prev_ev = calreprod_allevents[_n-1] if _n > 1 by sample calid: gen prev_ev_dur = ev_dur[_n-1] if _n > 1 - Capture the following event and its duration
-
by sample calid: gen calreprod_next_ev = calreprod_allevents[_n+1] if _n < _N by sample calid: gen next_ev_dur = ev_dur[_n+1] if _n < _N - Generate CMC (century month code) for start and end of event
-
by sample calid: gen calcmc_ev_start = calcmc_month - ev_dur + 1 rename calcmc_month calcmc_ev_end order calcmc_ev_start, before(calcmc_ev_end)
Step 7. Naming, tidying up, and saving the event file
- Label the variables and values
-
label variable calcmc_ev_start "CMC start of the event" label variable calcmc_ev_end "CMC end of the event" label variable ev_number "Event's number" label variable ev_dur "Duration of event" label variable calreprod_prev_ev "Prior reproductive event" label variable prev_ev_dur "Duration of prior event" label variable calreprod_next_ev "Next reproductive event" label variable next_ev_dur "Duration of next event" label def event /// check list is completed - may change by sample 0 "no contraceptive use" /// 1 "pill" /// 2 "iud" /// 3 "condom" /// 4 "female sterilization" /// 5 "male sterilization" /// 6 "withdrawal" /// 7 "female condom" /// 8 "emergency contraception" /// 9 "lactational amenorrhea/breastfeeding" /// 10 "implants/norplant" /// 20 "injection" /// 32 "foam or jelly" /// 41 "periodic abstinence/rhythm" /// 42 "standard days method" /// 50 "other modern methods" /// 60 "other traditional methods" /// 100 "birth" /// 200 "pregnancy" /// 300 "termination" label val calreprod_prev_ev event label val calreprod_next_ev event drop new_ev tot_ev - To restore the original order of observations
-
sort order - Save the event file
-
save eventsfile.dta replace
An example:
To analyze the event file, we can quickly calculate the reason for contraceptive discontinuation in the last five years by method
tab calreason calreprod_allevents [iw=perweight] if calreason != 99 & intdatecmc-calcmc_ev_end < 60, col
--------------------
| Key |
-------------------
| frequency |
|column percentage |
-------------------
reason for |
discontinuation of | numeric recode of reproductive events for woman-month
contraceptive | pill iud condom withdrawa female co emergency lactation implants/ injection periodic | Total
----------------------+--------------------------------------------------------------------------------------------------------------------------------
became pregnant while | 26.160196 5.719049 7.000938 52.570238 1.051848 1.380446 3.359962 2.998076 29.993315 70.716725 | 234.186335
| 8.30 2.71 4.50 20.48 84.85 9.18 15.39 0.45 1.45 35.17 | 5.87
----------------------+--------------------------------------------------------------------------------------------------------------------------------
wanted to become preg | 78.580688 87.361426 34.021649 87.320845 .187762 1.706077 9.483768 200.030927 638.743528 79.423568 | 1,238.017
| 24.94 41.37 21.89 34.01 15.15 11.35 43.45 30.31 30.95 39.50 | 31.03
-------------------------------------------------------------------------------------------------------------------------------------------------------
husband disapproved | 9.517945 2.505612 18.717995 32.112938 0 .704056 1.432549 7.698788 46.155641 10.234959 | 132.505496
| 3.02 1.19 12.04 12.51 0.00 4.68 6.56 1.17 2.24 5.09 | 3.32
-------------------------------------------------------------------------------------------------------------------------------------------------------
lack of access/availa | 1.33521 0 3.323564 0 0 0 1.481831 2.163824 20.685938 0 | 28.988678
| 0.42 0.00 2.14 0.00 0.00 0.00 6.79 0.33 1.00 0.00 | 0.73
-------------------------------------------------------------------------------------------------------------------------------------------------------
cost | 0 0 1.292885 0 0 0 0 1.188386 0 0 | 2.481271
| 0.00 0.00 0.83 0.00 0.00 0.00 0.00 0.18 0.00 0.00 | 0.06
-------------------------------------------------------------------------------------------------------------------------------------------------------
fatalistic | 3.830159 6.190334 0 0 0 0 0 15.484339 25.171299 0 | 50.676131
| 1.22 2.93 0.00 0.00 0.00 0.00 0.00 2.35 1.22 0.00 | 1.27
-------------------------------------------------------------------------------------------------------------------------------------------------------
side effects |109.140817 66.26268 8.852992 .804099 0 5.540994 0 289.941605 841.771695 0 | 1,324.944
| 34.64 31.38 5.70 0.31 0.00 36.87 0.00 43.93 40.79 0.00 | 33.21
-------------------------------------------------------------------------------------------------------------------------------------------------------
wanted more effective | 21.020382 10.753556 18.694208 25.120335 0 1.510642 1.000309 38.625556 106.964656 6.737573 | 236.282917
| 6.67 5.09 12.03 9.78 0.00 10.05 4.58 5.85 5.18 3.35 | 5.92
-------------------------------------------------------------------------------------------------------------------------------------------------------
inconvenient to use | 14.32757 7.024353 14.57675 16.236289 0 0 0 21.358232 49.797218 12.989205 | 139.739624
| 4.55 3.33 9.38 6.32 0.00 0.00 0.00 3.24 2.41 6.46 | 3.50
-------------------------------------------------------------------------------------------------------------------------------------------------------
infrequent sex/husban | 10.130525 10.719979 25.544178 8.81291 0 2.737666 2.546294 15.56093 93.737817 3.418144 | 178.082551
| 3.22 5.08 16.43 3.43 0.00 18.22 11.66 2.36 4.54 1.70 | 4.46
-------------------------------------------------------------------------------------------------------------------------------------------------------
difficult to get preg | 0 3.491 .425002 0 0 0 0 2.400139 7.303679 0 | 13.61982
| 0.00 1.65 0.27 0.00 0.00 0.00 0.00 0.36 0.35 0.00 | 0.34
-------------------------------------------------------------------------------------------------------------------------------------------------------
marital dissolution | 8.166641 1.230794 2.688733 .70605 0 0 0 4.275521 38.045966 0 | 55.113705
| 2.59 0.58 1.73 0.28 0.00 0.00 0.00 0.65 1.84 0.00 | 1.38
-------------------------------------------------------------------------------------------------------------------------------------------------------
other reason | 19.609398 7.724039 17.079134 6.764132 0 .202048 2.523998 49.844602 135.553324 6.265354 | 251.428352
| 6.22 3.66 10.99 2.63 0.00 1.34 11.56 7.55 6.57 3.12 | 6.30
-------------------------------------------------------------------------------------------------------------------------------------------------------
do not know | 13.256051 2.179981 3.219721 26.281595 0 1.247746 0 8.410382 29.732381 11.29803 | 104.008108
| 4.21 1.03 2.07 10.24 0.00 8.30 0.00 1.27 1.44 5.62 | 2.61
-------------------------------------------------------------------------------------------------------------------------------------------------------
Total | 315.073893 211.162803 155.437749 256.729431 1.23961 15.029675 21.828711 659.981307 2,063.656 201.083557 | 3,990.074
| 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 | 100.00
reason for | numeric recode of reproductive
discontinuation of | events for woman-month
contraceptive | standard other mod other tra | Total
-----------------------+-------------------------------------------------
became pregnant while | 28.844256 1.414886 2.976401 | 234.186335
| 39.13 60.03 23.29 | 5.87
-----------------------+-------------------------------------------------
wanted to become preg | 21.157221 0 0 | 1,238.017
| 28.70 0.00 0.00 | 31.03
-----------------------+-------------------------------------------------
husband disapproved | 3.425013 0 0 | 132.505496
| 4.65 0.00 0.00 | 3.32
-----------------------+-------------------------------------------------
lack of access/availa | 0 0 0 | 28.988678
| 0.00 0.00 0.00 | 0.73
-----------------------+-------------------------------------------------
cost | 0 0 0 | 2.481271
| 0.00 0.00 0.00 | 0.06
-----------------------+-------------------------------------------------
fatalistic | 0 0 0 | 50.676131
| 0.00 0.00 0.00 | 1.27
-----------------------+-------------------------------------------------
side effects | 2.62909 0 0 | 1,324.944
| 3.57 0.00 0.00 | 33.21
-----------------------+-------------------------------------------------
wanted more effective | 5.8557 0 0 | 236.282917
| 7.94 0.00 0.00 | 5.92
-----------------------+-------------------------------------------------
inconvenient to use | .800917 0 2.62909 | 139.739624
| 1.09 0.00 20.57 | 3.50
-----------------------+-------------------------------------------------
infrequent sex/husban | 4.874108 0 0 | 178.082551
| 6.61 0.00 0.00 | 4.46
-----------------------+-------------------------------------------------
difficult to get preg | 0 0 0 | 13.61982
| 0.00 0.00 0.00 | 0.34
-----------------------+-------------------------------------------------
marital dissolution | 0 0 0 | 55.113705
| 0.00 0.00 0.00 | 1.38
-----------------------+-------------------------------------------------
other reason | 0 0 5.862323 | 251.428352
| 0.00 0.00 45.86 | 6.30
-----------------------+-------------------------------------------------
do not know | 6.125526 .94215 1.314545 | 104.008108
| 8.31 39.97 10.28 | 2.61
-----------------------+-------------------------------------------------
Total | 73.711831 2.357036 12.782359 | 3,990.074
| 100.00 100.00 100.00 | 100.00
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