We are trying to do an individual level impact evaluation using experiments. The intervention who's impact we are studying was at the town level. Unfortunately, we do not have a baseline control group (town or individual). To identify a control group we are conducting a PSM at the town level to identify a control group of towns using nearest neighbor matching. Once we have pairs of control-treatment towns, we will randomly select pairs to conduct the individual-level experiment in.

This is a simplified version of the code we are using to identify the pairs.

pscore treated $pscore_controls, 
pscore (mypscore) comsup numblo(5) level(0.01) blockid(myblockid)

psmatch2 treated, pscore( mypscore ) caliper (.001) noreplace neighbor(1) 
**//nearest neighbor matching//**

gen pair = _id if _treated==0
replace pair = _n1 if _treated==1 
**//identifies the matched treated   
neighbor //**
bysort pair: egen paircount =count(pair)
tab paircount **//drop if !=2, if not 2 means no nearest neighbor was found in given caliper width- 119 of 157 treated towns matched//**

I have two questions:

  1. Given that the intervention was at the village level but our outcome of interest is at the individual level- is the above-mentioned method a sound way to identify a control group?
  2. The matching controls we are using are for 2010, the intervention was in 2015, the experiment will be in 2017/2018. We are assuming that since 2010 levels are informing our matching, they are pre-intervention and hence a sound way to identify a control group. Is there another way to identify a sound-control group?

Also posted at https://www.statalist.org/forums/forum/general-stata-discussion/general/1414208-identifying-control-group-ex-post-with-no-baseline-propensity-score

  • $\begingroup$ I am a bit confused. Will you have individual-level data from untreated towns? Or any untreated data from treated towns? $\endgroup$ – Dimitriy V. Masterov Oct 20 '17 at 18:11
  • $\begingroup$ We will have individual-level data from both treated and untreated towns..but all this data will be post-intervention data. We have no baseline individual-level data. $\endgroup$ – Fatima Alvi Oct 23 '17 at 4:19

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