Dear Statalisters,

I am working on a panel data set to uniquely identify respondents across time. IDs may change across time for same individuals. Therefore, there is a separate ID variable every year (ivid02, ivid04, ivid06 and ivid08). Since some IDs show up even at the wrong survey year, I wrote a code to duplicate an existing ID only for the relevant survey year. However, I have noticed that Stata is not replicating the exact same IDs. For example, when I code

Code:
gen nivid02=.
replace nivid02=ivid02 if ivid02 !=. & survey==2002
format nivid02 %14.0f
I find nivid02 to be different from ivid02 across individuals.

How can I replicate existing IDs into new variables?

Please find below my sample data
Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(survey nivid02) double(ivid02 ivid04 ivid06 ivid08) float age
2002 4.0147073e+13 40147071110204              .              . .  3
2002  5.030731e+13 50307310401902 50307310041202              . . 31
2002  8.191113e+13 81911130700502 81911130070302 81911130070302 . 50
2002  5.090321e+13 50903211401203 50903210141703              . .  1
2002  8.150103e+13 81501030500702              .              . . 35
2002  3.051917e+13 30519170301503 30519170031003              . . 16
2002  6.070303e+13 60703031500302 60703030150102              . . 31
2002  5.091131e+13 50911311000604              .              . . 12
2002  6.070303e+13 60703031510104              .              . .  2
2002  6.010301e+13 60103010710402              .              . . 33
2002   7.01193e+13 70119294602103              .              . . 12
2002  7.110537e+13 71105370410601              .              . . 29
2002  3.031717e+13 30317170710102              .              . . 46
2002  5.070525e+13 50705251600801 50705250160501              . . 38
2002  7.090104e+13 70901043701104 70901040370604              . . 36
2002  1.130309e+13 11303091202004              .              . .  6
2002  5.110123e+13 51101230800702              .              . . 74
2002  8.230117e+13 82301172710502              .              . . 33
2002  8.051527e+13 80515270601801              .              . . 56
2002  2.150547e+13 21505470910401              .              . . 40
2002  2.092121e+13 20921210202003              .              . .  7
2002  1.010703e+13 10107030302305              .              . .  3
2002  4.014371e+13 40143710401402              .              . . 31
2002  7.110521e+13 71105210301003              .              . . 33
2002  1.131925e+13 11319251400204              .              . . 12
2002  1.151143e+13 11511431400904 11511430140604              . .  5
2002  4.031775e+13 40317751501702              .              . . 25
2002  8.031701e+13 80317010201803              .              . . 32
2002  2.011715e+13 20117150201103              .              . .  1
2002  2.171521e+13 21715211301303              .              . . 10
2002  8.131517e+13 81315171201106 81315170120706 81315170120705 .  6
2002  5.091101e+13 50911012401306 50911010240904 50911010240904 . 18
2002  6.052515e+13 60525150210306 60525150471406              . . 12
2002  2.070921e+13 20709210400205              .              . . 71
2002  2.251217e+13 22512170100403              .              . .  4
2002  2.051717e+13 20517170900801              .              . . 70
2002  8.091101e+13 80911011110501              .              . . 68
2002  3.031323e+13 30313230401007              .              . . 70
2002  7.170501e+13 71705010710303 71705010071302              . . 17
2002  8.190109e+13 81901090101602              .              . . 32
2002  5.110245e+13 51102451201301              .              . . 56
2002  5.110245e+13 51102451200701 51102450120701 51102450120701 . 45
2002  5.110131e+13 51101311500601              .              . . 36
2002  5.110245e+13 51102451200805 51102450120805 51102450120805 . 10
2002  5.110245e+13 51102451200806 51102450120806 51102450120806 .  5
2002  5.110245e+13 51102451210305              .              . . 10
2002 8.2301195e+13 82301191002006 82301190101304 82301190101305 . 13
2002  6.051719e+13 60517190401705 60517190351005              . .  6
2002  2.010707e+13 20107070501001 20107070050601              . . 39
2002  5.110245e+13 51102451200202 51102450120202 51102450120202 . 40
2002  1.151117e+13 11511170701602              .              . . 73
2002  8.051907e+13 80519070500703              .              . . 19
2002  8.190537e+13 81905372600202              .              . . 27
2002 1.0505532e+13 10505531600101              .              . . 52
2002  8.130516e+13 81305153600101              .              . . 64
2002  5.031733e+13 50317330301701              .              . . 48
2002  2.070913e+13 20709130400504              .              . . 11
2002  8.070931e+13 80709311210105              .              . . 18
2002  7.011713e+13 70117130500908              .              . . 40
2002  8.210709e+13 82107091514001              .              . . 32
2002  7.050113e+13 70501131500702              .              . . 26
2002  2.171955e+13 21719550300501 21719550030401 21719550030401 . 52
2002  8.170319e+13 81703190910408              .              . .  7
2002  4.050113e+13 40501130710101              .              . . 44
2002  5.110245e+13 51102451200301 51102450120301 51102450120301 . 61
2002  8.132105e+13 81321050502507              .              . . 14
2002  5.110117e+13 51101171002007              .              . .  1
2002  3.010715e+13 30107150210108 30107150161506 30107150021505 .  4
2002  6.053203e+13 60532031601601              .              . . 32
2002  8.150105e+13 81501051310504              .              . . 24
2002  5.050933e+13 50509330502203 50509330051003 50509330051003 .  8
2002  5.110245e+13 51102451210102 51102450121602 51102450121302 . 67
2002  5.110245e+13 51102451200502 51102450120502 51102450120501 . 37
2002 1.0403431e+13 10403431300101 10403430130101 10403430130101 . 30
2002  6.030123e+13 60301230510102 60301230051302              . . 36
2002  8.130517e+13 81305170200903              .              . . 25
2002  5.110245e+13 51102451200304              .              . . 21
2002  3.010305e+13 30103050902001 30203030091201              . . 29
2002  5.110245e+13 51102451201304              .              . . 18
2002  8.070705e+13 80707053200303              .              . . 25
2002  8.050103e+13 80501030900704              .              . . 20
2002  2.211723e+13 22117230800606              .              . . 27
2002  6.031113e+13 60311130600906              .              . .  8
2002  5.110147e+13 51101471001003              .              . .  9
2002  8.150121e+13 81501210800203              .              . . 34
2002  8.230501e+13 82305010800203              .              . .  9
2002  5.110245e+13 51102451201604 51102450121504              . . 14
2002  6.070307e+13 60703070200904              .              . . 11
2002  8.170511e+13 81705110700703              .              . . 17
2002  3.011723e+13 30117231500205 30213230150205              . . 11
2002 1.0119051e+13 10119050510204              .              . . 27
2002 8.0127094e+13 80127091010402              .              . . 40
2002  1.110735e+13 11107351100504 11107350111204              . .  6
2002  8.031325e+13 80313250200510              .              . . 17
2002  4.051525e+13 40515250410505              .              . . 12
2002  5.110253e+13 51102530600905              .              . .  6
2002  2.210935e+13 22109352701202              .              . . 44
2002  8.150915e+13 81509152201601              .              . . 36
2002  7.131535e+13 71315351601306              .              . .  1
2002  7.110529e+13 71105290400405 71105290041305 71105290041305 .  8
end