Missing data Treatment in STATA - Zero or Blank

[Annur Wijayakusuma]

Dear Statalist,

I tried to find the thread of missing data treatment in STATA but I could not find it. If someone has had the same question about this before, please kindly help me to post the link and happy to delete this thread.
I have questions regarding the missing data treatment in STATA for unbalanced panel data. I have unbalanced panel data for the period 2006 - 2017 with 5 variables. There are some years of some individual data that only have less than 5 variables, in that case:
1. how do I treat the missing data whether I need to put zero or leave it blank?
2. Whether put zero or leave it blank affect the number of observations?

What is the suggestion to treat this missing data? Here I list some of my datasets. The blank spot is the missing data.
Some years of ID has no data, do I need to take it off from my data or leave it blank or zero?

 
ID
Year
ROA
RD Intensity
Leverage
SIZE

ATM.AX
2017
          0.05018
        0.00593
        0.38395
        9.45276

ATM.AX
2016
          0.02428
        0.00573
        0.38600
        9.48925

ATM.AX
2015
          0.00314
        0.00360
        0.39662
        9.48102

ATM.AX
2014
          0.03123
        0.00312
        0.45238
        9.33767

ATM.AX
2013
          0.05913
        0.00711
        0.41489
        9.30480

ATM.AX
2012
          0.08257
        0.00865
        0.34890
        9.29429

ATM.AX
2011
          0.18975
        0.00940
        0.29137
        9.21509

ATM.AX
2010
          0.23416
        0.01478
        0.21568
        9.12382

ATM.AX
2009
          0.13495
        0.00739
        0.17878
        9.06997

ATM.AX
2008
          0.24983
        0.01419
        0.21297
        9.12548

ATM.AX
2007
          0.60715
        0.00504
        0.27347
        9.16574

ATM.AX
2006
          0.39480
        0.00567
        0.41285
        9.01221

CGM.AX
2017
-         0.35130

        3.24652
        6.26208

CGM.AX
2016
-         0.52461

        4.40949
        6.01259

CGM.AX
2015
-         2.31306

        2.22907
        6.19635

CGM.AX
2014
-         0.43015

        0.50321
        6.69391

CGM.AX
2013
-         0.19008

        0.78025
        6.72938

CGM.AX
2012
-         0.02078

        0.23537
        7.23147

CGM.AX
2011
          0.43734

        0.20769
        7.13459

CGM.AX
2010
-         0.15499
        0.26446
        0.22807
        6.97070

CGM.AX
2009
-         0.13175

        0.32719
        6.94133

CGM.AX
2008
-         0.02141
        0.63914
        0.22383
        6.94586

CGM.AX
2007
-         0.14034
      10.80597
        0.08406
        6.92174

CGM.AX
2006
          0.42961
        0.37287
        0.08025
        6.85449

CDT.AX
2017
-         1.34157
    109.61333
        0.94394
        5.53619

CDT.AX
2016
-         1.24766
      95.94615
        2.34886
        5.38998

CDT.AX
2015
-         0.78376
      60.82037
        0.90781
        5.67502

CDT.AX
2014
-         0.33934
      40.87309
        0.18513
        5.94838

CDT.AX
2013
-         0.21600
      17.59932
        0.07845
        6.36504

CDT.AX
2012
-         0.12898
      11.43324
        0.14042
        6.62093

CDT.AX
2011
-         0.01636
      10.52734
        0.11270
        6.94857

CDT.AX
2010
-         0.07897
      15.32129
        0.11668
        6.89607

CDT.AX
2009
-         0.74828
      19.32075
        0.11954
        5.93952

CDT.AX
2008
-         0.16633
      11.89941
        0.07615
        6.17522

CDT.AX
2007
-         0.16301
      13.50769
        0.05610
        6.39094

CDT.AX
2006
-         0.04072
      10.54762
        0.08028
        6.53631

ACS.AX
2017
-         0.07611

        0.70817
        6.80636

ACS.AX
2016
-         0.07500
        0.33179
        0.49811
        6.82299

ACS.AX
2015
-         0.13106
      31.48739
        0.04227
        6.68935

ACS.AX
2014
-         0.03868
      14.71475
        0.01227
        7.27406

ACS.AX
2013
-         0.03229

        0.01363
        7.33274

ACS.AX
2012
-         0.07118

        0.01272
        7.34673

ACS.AX
2011
-         0.03968

        0.00872
        7.34515

ACS.AX
2010
-         0.08017
        0.06501
        0.03051
        7.23339

ACS.AX
2009
-         0.04066
        2.17783
        0.01876
        7.08472

ACS.AX
2008
-         0.05734
        0.24290
        0.05078
        7.14192

ACS.AX
2007
-         0.10324
        3.48837
        0.02731
        6.65360

ACS.AX
2006
-         0.06944
        0.50633
        0.04601
        6.67560

MTB.AX
2017
-         0.46659

        4.31521
        5.91632

MTB.AX
2016
-         1.48764

      18.66129
        5.25057

MTB.AX
2015
-       33.69375

    156.65259
        4.27207

MTB.AX
2014
-       33.54684

      97.25403
        4.36078

MTB.AX
2013
-         1.49375

        3.09969
        5.71634

MTB.AX
2012
-         0.05620

        0.08268
        7.17762

MTB.AX
2011
-         0.06945
    359.63636
        0.04685
        7.17107

MTB.AX
2010
-         0.05665

        0.03956
        7.16164

MTB.AX
2009
-         0.05762

        0.01507
        7.17598

MTB.AX
2008
-         0.06749

        0.01717
        7.18021

MTB.AX
2007
-         0.08237

        0.00842
        7.13152

MTB.AX
2006
-         0.07369

        0.01274
        7.12516

RBX.AX
2017
-         0.67787
        0.57170
        1.41164
        6.05710

RBX.AX
2016
-         0.53093

        1.06794
        6.07142

RBX.AX
2015
-         0.27682

        0.61718
        6.26085

RBX.AX
2014
          0.59806

        0.65958
        6.55228

RBX.AX
2013
          0.03015

        0.82058
        6.61416

RBX.AX
2012
-         0.07778

        0.17023
        6.98062

RBX.AX
2011
-         0.06555

        0.17739
        6.84316

RBX.AX
2010
-         0.07915

        0.18446
        6.86146

RBX.AX
2009
-         0.18015

        0.18693
        6.82210

RBX.AX
2008
-         0.13902

        0.15665
        6.88098

RBX.AX
2007
-         0.14644

        0.39943
        6.24428

RBX.AX
2006





AKN.AX
2017
-         2.21257
        9.37860
        0.65464
        5.71814

AKN.AX
2016
-         0.42054
      10.84888
        0.04111
        6.35441

AKN.AX
2015
-         0.24696
        8.49135
        0.07540
        6.67257

AKN.AX
2014
-         0.05663
        5.50973
        0.06334
        7.16439

AKN.AX
2013
-         0.09448
        1.93775
        0.19924
        7.30691

AKN.AX
2012
-         0.11980
        0.67456
        0.06165
        7.23711

AKN.AX
2011
-         0.06847
        0.36629
        0.02397
        7.28684

AKN.AX
2010
-         0.15152
        0.99484
        0.05889
        6.86693

AKN.AX
2009
-         0.11908

        0.08859
        6.79574

AKN.AX
2008
-         0.06196

        0.04093
        6.82752

AKN.AX
2007
-         0.05565

        0.00892
        5.65072

AKN.AX
2006
-         0.02909

        0.01091
        5.43933

MRR.AX
2017
-         0.41977
      12.77106
        0.03207
        6.06567

MRR.AX
2016
-         0.86230
        7.58261
        0.09964
        5.95268

MRR.AX
2015
-         0.28658
        7.83351
        0.01687
        6.19640

MRR.AX
2014
-         0.18326

        0.01228
        6.36798

MRR.AX
2013
-         0.10291
        0.02852
        0.01068
        6.44262

MRR.AX
2012
-         0.07261
        2.82760
        0.00668
        6.48504

MRR.AX
2011


        0.03515
        5.24366

MRR.AX
2010





MRR.AX
2009





MRR.AX
2008





MRR.AX
2007





MRR.AX
2006





TRM.AX
2017
-         0.00422

        0.09956
        6.91081

TRM.AX
2016
-         0.00851
        0.06882
        0.08899
        6.89308

TRM.AX
2015
-         0.02591
        1.28617
        0.11003
        6.88303

TRM.AX
2014
-         0.03620

        0.09821
        6.87623

TRM.AX
2013
-         0.02435
        0.62122
        0.03535
        6.86844

TRM.AX
2012
          0.00418
        0.06506
        0.04045
        6.87061

TRM.AX
2011
          0.04336

        0.04025
        6.82295

TRM.AX
2010
          0.05312
        0.16829
        0.05570
        6.62582

TRM.AX
2009
-         0.10229
        0.59130
        0.04418
        6.52697

TRM.AX
2008
-         0.06111
        1.16660
        0.03922
        6.56055

TRM.AX
2007
-         0.07484

        0.00379
        6.51358

TRM.AX
2006
-         0.21166

        0.00648
        5.66558

SHK.AX
2017
-         0.14767

        3.02297
        7.23899

SHK.AX
2016
-         0.07280

        2.12392
        7.35471

SHK.AX
2015
-         0.11958

        1.94563
        7.34713

SHK.AX
2014
-         0.40082

        1.68499
        7.36349

SHK.AX
2013
-         0.24143
        0.15239
        1.13386
        7.32706

SHK.AX
2012
-         0.14063
        0.01212
        0.55371
        7.42744

SHK.AX
2011
          0.10056
        0.00545
        0.65543
        7.49603

SHK.AX
2010
-         0.14991
        0.02313
        0.25847
        7.54994

SHK.AX
2009
-         0.06999
      14.89601
        0.06047
        7.25310

SHK.AX
2008
-         0.03764

        0.01818
        7.27437

SHK.AX
2007
-         0.01666

        0.01383
        7.22076

SHK.AX
2006
          0.04023

        0.05745
        7.06288

MMG.AX
2017
          0.13883

        0.91809
      10.27781

MMG.AX
2016
          0.06050

        0.93234
      10.32446

MMG.AX
2015
          0.02870

        0.95453
      10.30430

MMG.AX
2014
          0.05715

        0.87500
      10.21790

MMG.AX
2013
          0.16039

        0.65408
        9.72055

MMG.AX
2012
          0.16209

        0.66398
        9.64239

MMG.AX
2011
          0.26854
        0.02872
        0.58436
        9.52860

MMG.AX
2010
          0.29721
        0.02891
        0.86241
        9.53121

MMG.AX
2009
          0.12214
        0.00612
        0.63062
        9.53984

MMG.AX
2008
          0.04663

        0.31626
        9.21098

MMG.AX
2007
          0.10341

        0.27585
        9.10573

MMG.AX
2006
          0.20649

        0.47994
        9.12186

KGD.AX
2017
-         0.07527

        0.00800
        6.99974

KGD.AX
2016
-         0.01410

        0.05045
        7.55888

KGD.AX
2015
-         0.01947

        0.01003
        7.62825

KGD.AX
2014
-         0.02176

        0.00987
        7.84639

KGD.AX
2013
-         0.01517

        0.02718
        8.06246

KGD.AX
2012
-         0.02362
      52.75198
        0.01679
        8.05634

KGD.AX
2011
-         0.00976

        0.02900
        8.14750

KGD.AX
2010
-         0.03316

        0.03259
        8.08258

KGD.AX
2009


        0.02380
        7.78115

KGD.AX
2008
-         0.01001

        0.02954
        7.79492

KGD.AX
2007





KGD.AX
2006





E3S.AX
2017


      48.76815
        4.38453

E3S.AX
2016


        5.54055
        5.43772

E3S.AX
2015
          0.00324
        2.35849
        1.83557
        5.88703

E3S.AX
2014
          0.06687
      26.14904
        0.92771
        5.91031

E3S.AX
2013
          1.38957
      40.73786
        0.52644
        5.99307

E3S.AX
2012
          0.18993
        0.23310
        0.03875
        6.35597

E3S.AX
2011


        0.05319
        6.56573

E3S.AX
2010


        0.24573
        6.39863

E3S.AX
2009
-         0.27949
        0.02500
        0.17656
        6.43616

E3S.AX
2008
-         0.08384
      17.55000
        0.09748
        6.80489

E3S.AX
2007
-         0.06442
        6.37931
        0.12511
        6.75089

E3S.AX
2006
-         0.03660

        0.16215
        6.95236

Look forward to helping me with this from the STATAlist forum.

Thanks,

Annur

[Clyde Schechter]

While it is possible to represent missing values with 0 (or, for that matter, any number you wish) in Stata, it is almost always a terrible idea to do so.

You show a listing of some data, that comes from some source other than a Stata data set -- I know that because RD Intensity is not a legal variable name in Stata. There are various Stata commands, and for that matter, other file conversion programs, that can create a Stata data set from many types of non-Stata original sources. You will need to do that before you can do anything else with your data in Stata. All the ones that I'm familiar with will automatically fill in the "blanks" with Stata's internal missing value representation--in fact I don't even know of any that give you the option of doing anything else. If you have some really good reason for overwriting that with a numerical value, once the data are imported into Stata you can do that--but as I have already said, and cannot emphasize strongly enough, it is very rarely a good idea to do that. Leave the Stata missing values alone unless you have a compelling reason to do otherwise.

When Stata then uses your data for analysis, it will appropriately handle missing values for you. In regression models, any observation (row of the data matrix) that contains a missing value for any variable mentioned in the regression is omitted from the regression calculations. The handling of missing values by Stata, if you leave them alone, is quite natural and produces sensible and useful results. (Well, some people think that in the context of logical expressions interpreting missing value as "true" is not so sensible and useful, but other than that...) By contrast, if you tamper with the data to replace missing values with zero, those values will be treated just like a real zero--which means you will be using false data and get false results. In short, unless you know that in the creation of the source data set its creators, for some peculiar reason, chose to leave out observations with value zero and just leave those blank, replacing them with zeroes will just contaminate your data set with errors and make everything you do with it wrong.

[Annur Wijayakusuma]

Hi Clyde,

Thanks for your comment.
regarding:

You show a listing of some data, that comes from some source other than a Stata data set

Yes, I copy the data from my excel spreadsheet instead of the STATA dataset. I was confused whether I leave it blank or zero if put it zero whether it affects the number of observations or not.

There are various Stata commands,...... All the ones that I'm familiar with will automatically fill in the "blanks" with Stata's internal missing value representation

I imported from Excel to STATA and found the blank one put as a dot (.) I assume it is blank. That is the reason whether I need to change to zero or leave it as black before importing to STATA. Whether the changes affect the number of observations?

Look forward to your reply

Regards,

Annur

[Carlo Lazzaro]

Annur:
1) if the value of your observation is zero, Stata considers it as an observed value and the related observation is included in the -e(sample)- (if you do not impose clauses that rules it out, such as -if-. qualifier);
2) if the values is reported as missing, Stata will apply listwise deletion and rule out the observation from -e(sample)-.

That said, your approach does not seem to consider the missing mechanisms underlying unobserved values (missing completely at random; missing at random; missing not at random) that are informative to decide how to deal with missing values (see -mi- entries in Stata .pdf manual).

[Annur Wijayakusuma]

Hi Carlo,

Thank you for your comment. It is a crystal clear explanation.

Cheers

Annur

[Clyde Schechter]

I imported from Excel to STATA and found the blank one put as a dot (.) I assume it is blank.

The dot you refer to is the way Stata displays missing values of numeric variables when it shows you the data. You should leave those alone. For string variables, missing values are displayed as blank.