Hi everybody

I am making an IV regression. When constructing my instrument set I make regression only on the initial observations for all of my id's. Then I obtain the residuals. After having done this I need the instrument set containing the residuals for the rest of my observations for each id. It is not possible for my to make the regression on the other observation because the information used In the regression is not available besides from the initial period observations.

So what I am doing is that I use the residuals from the initial observations regression on the rest of the observations for each id. My question is then what consequences this will have, and if there is literature where this has been done before to support me doing this?

Here is the dataex of som of my data to get a feel of what I have done. As you see I have taking the residuals from first observations on copied them for all other observation with that ID. If you have any question please feel free to ask.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input double(HHIDPN Waves) float(Mother_age_at_death Dad_age_at_death resid resid1)
    3010  1 75 80   52.21634   73.19397
    3010  2  .  .   52.21634   73.19397
    3010  3  .  .   52.21634   73.19397
    3010  4  .  .   52.21634   73.19397
    3010  5  .  .   52.21634   73.19397
    3010  6  .  .   52.21634   73.19397
    3010  7  .  .   52.21634   73.19397
    3010  8  .  .   52.21634   73.19397
    3010  9  .  .   52.21634   73.19397
    3010 10  .  .   52.21634   73.19397
10013010  1 69 53   42.85693   67.67946
10013010  3  .  .   42.85693   67.67946
10013010  4  .  .   42.85693   67.67946
10013010  5  .  .   42.85693   67.67946
10013010  6  .  .   42.85693   67.67946
10013010  7  .  .   42.85693   67.67946
10013010  8  .  .   42.85693   67.67946
10013010  9  .  .   42.85693   67.67946
10013010 10  .  .   42.85693   67.67946
10038010  1 50 66   44.70567   49.12651
10038010  3  .  .   44.70567   49.12651
10038010  4  .  .   44.70567   49.12651
10038010  5  .  .   44.70567   49.12651
10038010  6  .  .   44.70567   49.12651
10038010  7  .  .   44.70567   49.12651
10038010  8  .  .   44.70567   49.12651
10038010  9  .  .   44.70567   49.12651
10038010 10  .  .   44.70567   49.12651
10050010  1  0 74   43.94625  22.839033
10050010  3  .  .   43.94625  22.839033
10050010  4  .  .   43.94625  22.839033
10050010  5  .  .   43.94625  22.839033
10050010  6  .  .   43.94625  22.839033
10050010  7  .  .   43.94625  22.839033
10050010  8  .  .   43.94625  22.839033
10050010  9  .  .   43.94625  22.839033
10050010 10  .  .   43.94625  22.839033
10225010  1 82 45 -17.016924  -32.73683
10225010  2  .  . -17.016924  -32.73683
10225010  3  .  . -17.016924  -32.73683
10225010  5  .  . -17.016924  -32.73683
10225010  6  .  . -17.016924  -32.73683
10225010  7  .  . -17.016924  -32.73683
10225010  8  .  . -17.016924  -32.73683
10225010  9  .  . -17.016924  -32.73683
10225010 10  .  . -17.016924  -32.73683
10299010  1  0  0   22.37574  -16.85536
10299010  4  .  .   22.37574  -16.85536
10299010  5  .  .   22.37574  -16.85536
10299010  6  .  .   22.37574  -16.85536
10299010  7  .  .   22.37574  -16.85536
10299010  8  .  .   22.37574  -16.85536
10299010  9  .  .   22.37574  -16.85536
10299010 10  .  .   22.37574  -16.85536
10325020  1  0 52 -28.805786 -30.038923
10325020  3  .  . -28.805786 -30.038923
10325020  4  .  . -28.805786 -30.038923
10325020  5  .  . -28.805786 -30.038923
10325020  6  .  . -28.805786 -30.038923
10372010  1 71 73  -41.62628 -26.359983
10372010  3  .  .  -41.62628 -26.359983
10372010  4  .  .  -41.62628 -26.359983
10372010  5  .  .  -41.62628 -26.359983
10372010  6  .  .  -41.62628 -26.359983
10372010  7  .  .  -41.62628 -26.359983
10372010  8  .  .  -41.62628 -26.359983
10372010  9  .  .  -41.62628 -26.359983
10372010 10  .  .  -41.62628 -26.359983
10378010  1  0 70  -37.60967 -25.504025
10378010  4  .  .  -37.60967 -25.504025
10378010  5  .  .  -37.60967 -25.504025
10378010  6  .  .  -37.60967 -25.504025
10378010  7  .  .  -37.60967 -25.504025
10394010  1  0 66   50.56738   60.01219
10394010  4  .  .   50.56738   60.01219
10394010  5  .  .   50.56738   60.01219
10394010  6  .  .   50.56738   60.01219
10394010  7  .  .   50.56738   60.01219
10394010  8  .  .   50.56738   60.01219
10394010  9  .  .   50.56738   60.01219
10394010 10  .  .   50.56738   60.01219
10395010  1  0 70  -3.319559  17.950354
10395010  3  .  .  -3.319559  17.950354
10395010  4  .  .  -3.319559  17.950354
10395010  5  .  .  -3.319559  17.950354
10395010  6  .  .  -3.319559  17.950354
10395010  7  .  .  -3.319559  17.950354
10395010  8  .  .  -3.319559  17.950354
10395010  9  .  .  -3.319559  17.950354
10395020  1  0 83   19.40187 -18.756739
10395020  3  .  .   19.40187 -18.756739
10395020  4  .  .   19.40187 -18.756739
10395020  5  .  .   19.40187 -18.756739
10395020  7  .  .   19.40187 -18.756739
10395020  8  .  .   19.40187 -18.756739
10395020  9  .  .   19.40187 -18.756739
10395020 10  .  .   19.40187 -18.756739
10404010  1  0  0  -31.20806 -11.840034
10404010  2  .  .  -31.20806 -11.840034
10404010  3  .  .  -31.20806 -11.840034
end

Thank you very much

Kind regards

Mads