My data looks like this.
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Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long HHID_n float year
  1 2011
  3 2011
  4 2011
  5 2011
  7 2011
  8 2011
  9 2011
 10 2011
 11 2009
 12 2011
 13 2011
 14 2010
 15 2010
 16 2009
 17 2011
 18 2011
 19 2009
 20 2009
 21 2011
 22 2010
 23 2011
 24 2009
 25 2011
 26 2009
 27 2009
 28 2011
 29 2011
 30 2011
 31 2011
 32 2011
 33 2011
 34 2011
 35 2011
 36 2011
 37 2011
 38 2009
 39 2009
 40 2010
 41 2011
 42 2009
 43 2011
 44 2009
 45 2009
 46 2009
 47 2011
 48 2011
 49 2011
 50 2011
 51 2011
 52 2009
 53 2009
 54 2010
 55 2011
 56 2011
 57 2011
 58 2010
 59 2011
 60 2011
 61 2010
 62 2011
 63 2011
 64 2009
 65 2011
 66 2009
 67 2011
 68 2011
 69 2010
 70 2011
 71 2011
 72 2010
 73 2011
 74 2009
 75 2010
 76 2011
 77 2010
 78 2011
 79 2011
 80 2011
 81 2011
 82 2010
 83 2010
 84 2011
 85 2010
 86 2009
 87 2011
 88 2011
 89 2011
 90 2009
 91 2011
 92 2011
 93 2011
 94 2011
 95 2011
 96 2011
 97 2011
 98 2011
 99 2011
100 2011
101 2010
102 2011
end
label values HHID_n HHID_n
label def HHID_n 1 "1013000201", modify
label def HHID_n 3 "1013000204", modify
label def HHID_n 4 "1013000206", modify
label def HHID_n 5 "1013000210", modify
label def HHID_n 7 "101300021302", modify
label def HHID_n 8 "1021000102", modify
label def HHID_n 9 "1021000108", modify
label def HHID_n 10 "1021000111", modify
label def HHID_n 11 "1021000113", modify
label def HHID_n 12 "1021000201", modify
label def HHID_n 13 "1021000203", modify
label def HHID_n 14 "1021000204", modify
label def HHID_n 15 "1021000207", modify
label def HHID_n 16 "1021000209", modify
label def HHID_n 17 "1021000212", modify
label def HHID_n 18 "1021000213", modify
label def HHID_n 19 "1021000303", modify
label def HHID_n 20 "1021000310", modify
label def HHID_n 21 "1021000312", modify
label def HHID_n 22 "1021000402", modify
label def HHID_n 23 "1021000405", modify
label def HHID_n 24 "102100040502", modify
label def HHID_n 25 "1021000406", modify
label def HHID_n 26 "102100040606", modify
label def HHID_n 27 "1021000503", modify
label def HHID_n 28 "1021000504", modify
label def HHID_n 29 "1021000506", modify
label def HHID_n 30 "1021000604", modify
label def HHID_n 31 "1021000607", modify
label def HHID_n 32 "1021000608", modify
label def HHID_n 33 "1021000610", modify
label def HHID_n 34 "1021000612", modify
label def HHID_n 35 "1021000701", modify
label def HHID_n 36 "1021000702", modify
label def HHID_n 37 "1021000703", modify
label def HHID_n 38 "1021000705", modify
label def HHID_n 39 "1021000709", modify
label def HHID_n 40 "1021000710", modify
label def HHID_n 41 "1021000711", modify
label def HHID_n 42 "1021000802", modify
label def HHID_n 43 "1021000805", modify
label def HHID_n 44 "102100080503", modify
label def HHID_n 45 "1021000807", modify
label def HHID_n 46 "1021000810", modify
label def HHID_n 47 "1021000811", modify
label def HHID_n 48 "1021000906", modify
label def HHID_n 49 "1021001003", modify
label def HHID_n 50 "1021001004", modify
label def HHID_n 51 "1021001007", modify
label def HHID_n 52 "1021001008", modify
label def HHID_n 53 "1021001009", modify
label def HHID_n 54 "1021001011", modify
label def HHID_n 55 "1021001102", modify
label def HHID_n 56 "1021001105", modify
label def HHID_n 57 "1021001107", modify
label def HHID_n 58 "1021001109", modify
label def HHID_n 59 "102100110901", modify
label def HHID_n 60 "102100110904", modify
label def HHID_n 61 "1021001110", modify
label def HHID_n 62 "1021001202", modify
label def HHID_n 63 "1021001205", modify
label def HHID_n 64 "1021001206", modify
label def HHID_n 65 "1021001208", modify
label def HHID_n 66 "1021001210", modify
label def HHID_n 67 "1021001211", modify
label def HHID_n 68 "1021001302", modify
label def HHID_n 69 "1021001304", modify
label def HHID_n 70 "1021001306", modify
label def HHID_n 71 "1021001308", modify
label def HHID_n 72 "1021001309", modify
label def HHID_n 73 "1021001402", modify
label def HHID_n 74 "102100140202", modify
label def HHID_n 75 "1021001403", modify
label def HHID_n 76 "1021001405", modify
label def HHID_n 77 "1021001406", modify
label def HHID_n 78 "1021001407", modify
label def HHID_n 79 "1021001408", modify
label def HHID_n 80 "1021001501", modify
label def HHID_n 81 "1021001504", modify
label def HHID_n 82 "102100150406", modify
label def HHID_n 83 "1021001505", modify
label def HHID_n 84 "1021001507", modify
label def HHID_n 85 "102100160707", modify
label def HHID_n 86 "1021001610", modify
label def HHID_n 87 "1021001701", modify
label def HHID_n 88 "1021001704", modify
label def HHID_n 89 "1021001705", modify
label def HHID_n 90 "1021001706", modify
label def HHID_n 91 "1021001709", modify
label def HHID_n 92 "1021001710", modify
label def HHID_n 93 "102100171003", modify
label def HHID_n 94 "1021001713", modify
label def HHID_n 95 "1021001804", modify
label def HHID_n 96 "1021001809", modify
label def HHID_n 97 "1021001810", modify
label def HHID_n 98 "1021001902", modify
label def HHID_n 99 "1021001907", modify
label def HHID_n 100 "1021001908", modify
label def HHID_n 101 "1021001909", modify
label def HHID_n 102 "1021001910", modify
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Would weakly balanced panel be a problem in estimation? Thank you!