how to assign the value of a variable for each cotrol firm according to the value of its matched treatment firm

[Alice Yang]

Dear statalist,

I have a set of variables, firm, year, treat, disclosuredate, _id, and _n1. treat is a dummy to indicate whether the firm is subject to a certain treatment; the disclosuredate variable is only available for treatment firms. I use 1 to 1 nearest neighbor matching with replacement to match each control firm to a treatment firm, because disclosuredate variable is missing for control firms, I want to use the disclosuredate of the matched treatment firm to substitute the missing value for the corresponding control firm. From the PSM procedure, I have _id, which represents the identifier from psmatch2, and _n1, which is the ID of nearest neighbor nr. 1.

This sample spans two years, from 2019 to 2020. The sample is perfectly balanced, each firm has an observation in both 2019 and 2020.

I wonder what is the code that can help me to substitute the missing value of disclosuredate for each control firm using the value of its matched treatment firm. Thanks a lot for any kind help!

Here are some data

* Example generated by -dataex-. For more info, type help dataex
clear
input double firm float(year disclosuredate treat) int(_id _n1)
150 2019     . 0 1419 2418
150 2020     . 0 1284 2375
153 2019     . 0  583 2175
153 2020     . 0  868 2271
156 2019 21949 1 2534 1751
156 2020 21949 1 2557 1818
157 2019     . 0 1757 2535
157 2020     . 0 1876 2578
159 2019     . 0  530 2169
159 2020     . 0  600 2179
166 2019     . 0 1934 2604
166 2020     . 0 1944 2610
338 2019     . 0 1798 2548
338 2020     . 0 1831 2562
400 2019     . 0 1514 2447
400 2020     . 0 1708 2514
403 2019     . 0 1683 2508
403 2020     . 0 1887 2583
408 2019     . 0 1677 2507
408 2020     . 0 1762 2536
411 2019 21949 1 2289  953
411 2020 21949 1 2387 1349
415 2019     . 0 1817 2554
415 2020     . 0 1750 2534
419 2019     . 0  764 2231
419 2020     . 0  913 2277
420 2019     . 0 1780 2540
420 2020     . 0 1795 2548
422 2019 21938 1 2314 1015
422 2020 21938 1 2351 1200
423 2019     . 0 1874 2578
423 2020     . 0 1907 2588
428 2019     . 0  777 2242
428 2020     . 0  936 2285
430 2019     . 0 1225 2362
430 2020     . 0 1297 2377
488 2019     . 0 1690 2508
488 2020     . 0 1793 2547
501 2019 21937 1 2552 1808
501 2020 21937 1 2558 1826
509 2019     . 0 1622 2486
509 2020     . 0 1777 2540
516 2019     . 0 1489 2441
516 2020     . 0 1853 2569
517 2019 21949 1 2566 1839
517 2020 21949 1 2576 1868
519 2019     . 0 1355 2388
519 2020     . 0 1557 2463
520 2019 21937 1 2507 1678
520 2020 21937 1 2505 1671
526 2019     . 0 1397 2411
526 2020     . 0 1703 2513
528 2019     . 0 1693 2510
528 2020     . 0 1744 2533
534 2019     . 0 1628 2488
534 2020     . 0 1805 2550
536 2019 21949 1 2422 1431
536 2020 21949 1 2471 1580
544 2019 21949 1 2368 1252
544 2020 21949 1 2406 1391
545 2019     . 0 1669 2503
545 2020     . 0 1768 2537
546 2019     . 0 1125 2339
546 2020     . 0 1062 2325
547 2019 21949 1 2569 1850
547 2020 21949 1 2619 1952
553 2019 21938 1 2481 1604
553 2020 21938 1 2464 1563
554 2019     . 0 1245 2368
554 2020     . 0 1290 2376
558 2019 21949 1 2561 1831
558 2020 21949 1 2563 1837
559 2019 21949 1 2541 1785
559 2020 21949 1 2571 1857
561 2019     . 0 1583 2472
561 2020     . 0 1653 2499
563 2019     . 0 1969 2622
563 2020     . 0 1970 2622
564 2019     . 0 1545 2462
564 2020     . 0 1671 2505
568 2019     . 0 1963 2621
568 2020     . 0 1995 2631
576 2019     . 0 1420 2418
576 2020     . 0 1649 2495
582 2019     . 0 1639 2493
582 2020     . 0 1738 2530
584 2019     . 0 1584 2473
584 2020     . 0 1705 2513
590 2019     . 0 1400 2411
590 2020     . 0 1317 2382
592 2019 21949 1 2472 1582
592 2020 21949 1 2492 1638
596 2019     . 0 1866 2575
596 2020     . 0 1941 2609
601 2019     . 0 1535 2452
601 2020     . 0 1688 2508
606 2019     . 0 1168 2345
606 2020     . 0 1033 2319
607 2019 21949 1 2458 1540
607 2020 21949 1 2453 1536
end

[Hemanshu Kumar]

Consider:

tempfile main
save `main'

keep if treat == 1
keep _id disclosuredate
rename disclosuredate n1_disclosuredate
rename _id _n1

tempfile n1
save `n1'

use `main'
merge m:1 _n1 using `n1', keep(1 3)

which produces:

. list if _merge == 3, noobs sep(0) abbrev(20)

  +--------------------------------------------------------------------------------------+
  | firm   year   disclosuredate   treat    _id    _n1   n1_disclosuredate        _merge |
  |--------------------------------------------------------------------------------------|
  |  554   2019                .       0   1245   2368               21949   Matched (3) |
  |  561   2019                .       0   1583   2472               21949   Matched (3) |
  |  564   2020                .       0   1671   2505               21937   Matched (3) |
  |  408   2019                .       0   1677   2507               21937   Matched (3) |
  |  415   2020                .       0   1750   2534               21949   Matched (3) |
  |  516   2020                .       0   1853   2569               21949   Matched (3) |
  +--------------------------------------------------------------------------------------+

[Alice Yang]

Hi Hemanshu, thanks for your help, it works well!