Hello,

I have this data. I'm trying to run a placebo DiD. Pre-treatment =2018. Some of the drugs got treated in 2019, and others in 2020.

When I use this command random effect, I get some results. However, when I use fixed effects, all the drugs are omitted due to collinearity.


Code:
xtreg Tot_Clms treatment_indicator##year  year2019 i.civica_altrantive_code i.Gnrc_Name_code , vce(cluster civica_altrantive_code)
Any idea how to solve this issue??

Thank you,

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input str227 Brnd_Name str137 Gnrc_Name long Tot_Clms_2017 float date str137 civica_altrantive float(civica_date treatment_indicator t_2018 t_2019 t_2020) long(Gnrc_Name_code Brnd_Name_code civica_altrantive_code) float(year K id year2019 year2020)
"Actiq"                                          "Fentanyl Citrate"                71 2018 "Fentalyn & Morphin"          2019 0 1 0 0 42  1  7 0 -1  1 1 0
"Actiq"                                          "Fentanyl Citrate"                61 2019 "Fentalyn & Morphin"          2019 1 0 1 0 42  1  7 1  0  1 1 0
"Actiq"                                          "Fentanyl Citrate"                34 2020 "Fentalyn & Morphin"          2019 1 0 0 1 42  1  7 0  1  1 1 0
"Akten"                                          "Lidocaine HCl/PF"                53 2018 "Lidocaine"                   2019 0 1 0 0 52  2 10 0 -1  2 1 0
"Akten"                                          "Lidocaine HCl/PF"                89 2019 "Lidocaine"                   2019 1 0 1 0 52  2 10 1  0  2 1 0
"Akten"                                          "Lidocaine HCl/PF"                48 2020 "Lidocaine"                   2019 1 0 0 1 52  2 10 0  1  2 1 0
"Aldactone"                                      "Spironolactone"                2851 2018 "metoprolol Tartrate"         2019 0 1 0 0 72  3 18 0 -1  3 1 0
"Aldactone"                                      "Spironolactone"                2456 2019 "metoprolol Tartrate"         2019 1 0 1 0 72  3 18 1  0  3 1 0
"Aldactone"                                      "Spironolactone"                2084 2020 "metoprolol Tartrate"         2019 1 0 0 1 72  3 18 0  1  3 1 0
"Alembic Pharmac"                                "Famotidine"                  412649 2018 "Pantoprazole"                2020 0 1 0 0 39 72 13 0 -2  4 0 1
"Alembic Pharmac"                                "Famotidine"                  630009 2019 "Pantoprazole"                2020 0 0 1 0 39 72 13 0 -1  4 0 1
"Alembic Pharmac"                                "Famotidine"                 1782882 2020 "Pantoprazole"                2020 1 0 0 1 39 72 13 1  0  4 0 1
"American Antibi"                                "Amoxicillin"                     27 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2  5 0 1
"American Antibi"                                "Amoxicillin"                     27 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1  5 0 1
"American Antibi"                                "Amoxicillin"                     44 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0  5 0 1
"Amikacin Sulfate"                               "Amikacin Sulfate"             16532 2018 "Ampiciliin"                  2020 0 1 0 0  1  4  1 0 -2  6 0 1
"Amikacin Sulfate"                               "Amikacin Sulfate"             13442 2019 "Ampiciliin"                  2020 0 0 1 0  1  4  1 0 -1  6 0 1
"Amikacin Sulfate"                               "Amikacin Sulfate"             11600 2020 "Ampiciliin"                  2020 1 0 0 1  1  4  1 1  0  6 0 1
"Amitriptyline HCl"                              "Amitriptyline HCl"          3797915 2018 "Lorazepam"                   2020 0 1 0 0  2  5 19 0 -1  7 0 1
"Amitriptyline HCl"                              "Amitriptyline HCl"          3681732 2019 "Lorazepam"                   2020 1 0 1 0  2  5 19 0  0  7 0 1
"Amitriptyline HCl"                              "Amitriptyline HCl"          3755045 2020 "Lorazepam"                   2020 1 0 0 1  2  5 19 1  1  7 0 1
"Amoxapine"                                      "Amoxapine"                     3126 2018 "Lorazepam"                   2020 0 1 0 0  3  6 19 0 -1  8 0 1
"Amoxapine"                                      "Amoxapine"                     4047 2019 "Lorazepam"                   2020 1 0 1 0  3  6 19 0  0  8 0 1
"Amoxapine"                                      "Amoxapine"                     2934 2020 "Lorazepam"                   2020 1 0 0 1  3  6 19 1  1  8 0 1
"Amoxicillin,Aurobindo Pharm"                    "Amoxicillin"                1412964 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2  9 0 1
"Amoxicillin,Aurobindo Pharm"                    "Amoxicillin"                2341980 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1  9 0 1
"Amoxicillin,Aurobindo Pharm"                    "Amoxicillin"                1777946 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0  9 0 1
"Amoxicillin,Bi-Coastal Phar"                    "Amoxicillin"                   4621 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2 10 0 1
"Amoxicillin,Bi-Coastal Phar"                    "Amoxicillin"                    272 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1 10 0 1
"Amoxicillin,Bi-Coastal Phar"                    "Amoxicillin"                    211 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0 10 0 1
"Amoxicillin,Northstar Rx Ll"                    "Amoxicillin"                 534065 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2 11 0 1
"Amoxicillin,Northstar Rx Ll"                    "Amoxicillin"                 605909 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1 11 0 1
"Amoxicillin,Northstar Rx Ll"                    "Amoxicillin"                 596963 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0 11 0 1
"Amoxicillin,Rising Pharm"                       "Amoxicillin"                 672617 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2 12 0 1
"Amoxicillin,Rising Pharm"                       "Amoxicillin"                 760515 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1 12 0 1
"Amoxicillin,Rising Pharm"                       "Amoxicillin"                 782981 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0 12 0 1
"Amoxicillin,Sandoz"                             "Amoxicillin"                2054664 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2 13 0 1
"Amoxicillin,Sandoz"                             "Amoxicillin"                2312775 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1 13 0 1
"Amoxicillin,Sandoz"                             "Amoxicillin"                1990184 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0 13 0 1
"Amoxicillin,Teva USA"                           "Amoxicillin"                2444739 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2 14 0 1
"Amoxicillin,Teva USA"                           "Amoxicillin"                1370516 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1 14 0 1
"Amoxicillin,Teva USA"                           "Amoxicillin"                1236808 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0 14 0 1
"Amoxicillin,West-Ward/Hikma"                    "Amoxicillin"                 336622 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  4  7 14 0 -2 15 0 1
"Amoxicillin,West-Ward/Hikma"                    "Amoxicillin"                 380317 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  4  7 14 0 -1 15 0 1
"Amoxicillin,West-Ward/Hikma"                    "Amoxicillin"                 541682 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  4  7 14 1  0 15 0 1
"Amoxicillin-Clavulanate Pot ER,Dr.Reddy'S Lab"  "Amoxicillin/Potassium Clav"     223 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  8 14 0 -2 16 0 1
"Amoxicillin-Clavulanate Pot ER,Dr.Reddy'S Lab"  "Amoxicillin/Potassium Clav"     113 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  8 14 0 -1 16 0 1
"Amoxicillin-Clavulanate Pot ER,Dr.Reddy'S Lab"  "Amoxicillin/Potassium Clav"      47 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  8 14 1  0 16 0 1
"Amoxicillin-Clavulanate Pot ER,Sandoz"          "Amoxicillin/Potassium Clav"   13731 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  8 14 0 -2 17 0 1
"Amoxicillin-Clavulanate Pot ER,Sandoz"          "Amoxicillin/Potassium Clav"   15062 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  8 14 0 -1 17 0 1
"Amoxicillin-Clavulanate Pot ER,Sandoz"          "Amoxicillin/Potassium Clav"   14445 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  8 14 1  0 17 0 1
"Amoxicillin-Clavulanate Potass,Aurobindo Pharm" "Amoxicillin/Potassium Clav"  926899 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 18 0 1
"Amoxicillin-Clavulanate Potass,Aurobindo Pharm" "Amoxicillin/Potassium Clav" 1221369 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 18 0 1
"Amoxicillin-Clavulanate Potass,Aurobindo Pharm" "Amoxicillin/Potassium Clav" 1666963 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 18 0 1
"Amoxicillin-Clavulanate Potass,Dr.Reddy'S Lab"  "Amoxicillin/Potassium Clav"   18480 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 19 0 1
"Amoxicillin-Clavulanate Potass,Dr.Reddy'S Lab"  "Amoxicillin/Potassium Clav"    7901 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 19 0 1
"Amoxicillin-Clavulanate Potass,Dr.Reddy'S Lab"  "Amoxicillin/Potassium Clav"    2086 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 19 0 1
"Amoxicillin-Clavulanate Potass,Micro Labs USA," "Amoxicillin/Potassium Clav"   62387 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 20 0 1
"Amoxicillin-Clavulanate Potass,Micro Labs USA," "Amoxicillin/Potassium Clav"  274570 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 20 0 1
"Amoxicillin-Clavulanate Potass,Micro Labs USA," "Amoxicillin/Potassium Clav"  351507 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 20 0 1
"Amoxicillin-Clavulanate Potass,Morton Grove Ph" "Amoxicillin/Potassium Clav"    7131 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 21 0 1
"Amoxicillin-Clavulanate Potass,Morton Grove Ph" "Amoxicillin/Potassium Clav"   11142 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 21 0 1
"Amoxicillin-Clavulanate Potass,Morton Grove Ph" "Amoxicillin/Potassium Clav"    7672 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 21 0 1
"Amoxicillin-Clavulanate Potass,Northstar Rx Ll" "Amoxicillin/Potassium Clav"  512570 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 22 0 1
"Amoxicillin-Clavulanate Potass,Northstar Rx Ll" "Amoxicillin/Potassium Clav"  603123 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 22 0 1
"Amoxicillin-Clavulanate Potass,Northstar Rx Ll" "Amoxicillin/Potassium Clav"  502922 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 22 0 1
"Amoxicillin-Clavulanate Potass,Sandoz"          "Amoxicillin/Potassium Clav" 2794166 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 23 0 1
"Amoxicillin-Clavulanate Potass,Sandoz"          "Amoxicillin/Potassium Clav" 2320555 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 23 0 1
"Amoxicillin-Clavulanate Potass,Sandoz"          "Amoxicillin/Potassium Clav" 1151934 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 23 0 1
"Amoxicillin-Clavulanate Potass,Teva USA"        "Amoxicillin/Potassium Clav"  500764 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 24 0 1
"Amoxicillin-Clavulanate Potass,Teva USA"        "Amoxicillin/Potassium Clav"  265598 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 24 0 1
"Amoxicillin-Clavulanate Potass,Teva USA"        "Amoxicillin/Potassium Clav"  299806 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 24 0 1
"Amoxicillin-Clavulanate Potass,West-Ward/Hikma" "Amoxicillin/Potassium Clav"  147199 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5  9 14 0 -2 25 0 1
"Amoxicillin-Clavulanate Potass,West-Ward/Hikma" "Amoxicillin/Potassium Clav"  692029 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5  9 14 0 -1 25 0 1
"Amoxicillin-Clavulanate Potass,West-Ward/Hikma" "Amoxicillin/Potassium Clav"  595475 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5  9 14 1  0 25 0 1
"Anafranil"                                      "Clomipramine HCl"               469 2018 "Lorazepam"                   2020 0 1 0 0 24 10 19 0 -1 26 0 1
"Anafranil"                                      "Clomipramine HCl"               441 2019 "Lorazepam"                   2020 1 0 1 0 24 10 19 0  0 26 0 1
"Anafranil"                                      "Clomipramine HCl"               416 2020 "Lorazepam"                   2020 1 0 0 1 24 10 19 1  1 26 0 1
"Apokyn"                                         "Apomorphine HCl"               4136 2018 "Fentalyn & Morphin"          2019 0 1 0 0  7 11  7 0 -1 27 1 0
"Apokyn"                                         "Apomorphine HCl"               4423 2019 "Fentalyn & Morphin"          2019 1 0 1 0  7 11  7 1  0 27 1 0
"Apokyn"                                         "Apomorphine HCl"               4543 2020 "Fentalyn & Morphin"          2019 1 0 0 1  7 11  7 0  1 27 1 0
"App/Fresenius K"                                "Famotidine"                    1350 2018 "Pantoprazole"                2020 0 1 0 0 39 72 13 0 -2 28 0 1
"App/Fresenius K"                                "Famotidine"                    1473 2019 "Pantoprazole"                2020 0 0 1 0 39 72 13 0 -1 28 0 1
"App/Fresenius K"                                "Famotidine"                    1079 2020 "Pantoprazole"                2020 1 0 0 1 39 72 13 1  0 28 0 1
"App/Premierpro"                                 "Famotidine/PF"                  676 2018 "Pantoprazole"                2020 0 1 0 0 41 71 13 0 -2 29 0 1
"App/Premierpro"                                 "Famotidine/PF"                  459 2019 "Pantoprazole"                2020 0 0 1 0 41 71 13 0 -1 29 0 1
"App/Premierpro"                                 "Famotidine/PF"                  838 2020 "Pantoprazole"                2020 1 0 0 1 41 71 13 1  0 29 0 1
"Arixtra"                                        "Fondaparinux Sodium"            207 2018 "Bivalirudin"                 2020 0 1 0 0 45 12  3 0 -2 30 0 1
"Arixtra"                                        "Fondaparinux Sodium"            156 2019 "Bivalirudin"                 2020 0 0 1 0 45 12  3 0 -1 30 0 1
"Arixtra"                                        "Fondaparinux Sodium"            143 2020 "Bivalirudin"                 2020 1 0 0 1 45 12  3 1  0 30 0 1
"Augmentin"                                      "Amoxicillin/Potassium Clav"     147 2019 "Piperacillin and Tazobactam" 2020 0 0 1 0  5 13 14 0 -1 31 0 1
"Augmentin"                                      "Amoxicillin/Potassium Clav"      67 2020 "Piperacillin and Tazobactam" 2020 1 0 0 1  5 13 14 1  0 31 0 1
"Augmentin,Dr.Reddy'S Lab"                       "Amoxicillin/Potassium Clav"     173 2018 "Piperacillin and Tazobactam" 2020 0 1 0 0  5 13 14 0 -2 32 0 1
"Belbuca"                                        "Buprenorphine HCl"            51827 2018 "Fentalyn & Morphin"          2019 0 1 0 0  9 14  7 0 -1 33 1 0
"Belbuca"                                        "Buprenorphine HCl"           130068 2019 "Fentalyn & Morphin"          2019 1 0 1 0  9 14  7 1  0 33 1 0
"Belbuca"                                        "Buprenorphine HCl"           176630 2020 "Fentalyn & Morphin"          2019 1 0 0 1  9 14  7 0  1 33 1 0
"Betamethasone Acetate-Sod Phos*"                ""                            873303 2020 "Dexamethasone"               2019 1 0 0 1  . 15  6 0  1 34 1 0
"Bethkis"                                        "Tobramycin"                      45 2018 "Ampiciliin"                  2020 0 1 0 0 75 16  1 0 -2 35 0 1
"Bethkis"                                        "Tobramycin"                      48 2019 "Ampiciliin"                  2020 0 0 1 0 75 16  1 0 -1 35 0 1
"Bethkis"                                        "Tobramycin"                      53 2020 "Ampiciliin"                  2020 1 0 0 1 75 16  1 1  0 35 0 1
end
format %ty date
format %ty civica_date
label values Gnrc_Name_code Gnrc_Name_code
label def Gnrc_Name_code 1 "Amikacin Sulfate", modify
label def Gnrc_Name_code 2 "Amitriptyline HCl", modify
label def Gnrc_Name_code 3 "Amoxapine", modify
label def Gnrc_Name_code 4 "Amoxicillin", modify
label def Gnrc_Name_code 5 "Amoxicillin/Potassium Clav", modify
label def Gnrc_Name_code 7 "Apomorphine HCl", modify
label def Gnrc_Name_code 9 "Buprenorphine HCl", modify
label def Gnrc_Name_code 24 "Clomipramine HCl", modify
label def Gnrc_Name_code 39 "Famotidine", modify
label def Gnrc_Name_code 41 "Famotidine/PF", modify
label def Gnrc_Name_code 42 "Fentanyl Citrate", modify
label def Gnrc_Name_code 45 "Fondaparinux Sodium", modify
label def Gnrc_Name_code 52 "Lidocaine HCl/PF", modify
label def Gnrc_Name_code 72 "Spironolactone", modify
label def Gnrc_Name_code 75 "Tobramycin", modify
label values Brnd_Name_code Brnd_Name_code
label def Brnd_Name_code 1 "Actiq", modify
label def Brnd_Name_code 2 "Akten", modify
label def Brnd_Name_code 3 "Aldactone", modify
label def Brnd_Name_code 4 "Amikacin Sulfate", modify
label def Brnd_Name_code 5 "Amitriptyline HCl", modify
label def Brnd_Name_code 6 "Amoxapine", modify
label def Brnd_Name_code 7 "Amoxicillin", modify
label def Brnd_Name_code 8 "Amoxicillin-Clavulanate Pot ER", modify
label def Brnd_Name_code 9 "Amoxicillin-Clavulanate Potass", modify
label def Brnd_Name_code 10 "Anafranil", modify
label def Brnd_Name_code 11 "Apokyn", modify
label def Brnd_Name_code 12 "Arixtra", modify
label def Brnd_Name_code 13 "Augmentin", modify
label def Brnd_Name_code 14 "Belbuca", modify
label def Brnd_Name_code 15 "Betamethasone Acetate-Sod Phos*", modify
label def Brnd_Name_code 16 "Bethkis", modify
label def Brnd_Name_code 71 "Famotidine", modify
label def Brnd_Name_code 72 "Famotidine*", modify
label values civica_altrantive_code civica_altrantive_code
label def civica_altrantive_code 1 "Ampiciliin", modify
label def civica_altrantive_code 3 "Bivalirudin", modify
label def civica_altrantive_code 6 "Dexamethasone", modify
label def civica_altrantive_code 7 "Fentalyn & Morphin", modify
label def civica_altrantive_code 10 "Lidocaine", modify
label def civica_altrantive_code 13 "Pantoprazole", modify
label def civica_altrantive_code 14 "Piperacillin and Tazobactam", modify
label def civica_altrantive_code 18 "metoprolol Tartrate", modify
label def civica_altrantive_code 19 "Lorazepam", modify
------------------ copy up to and including the previous line ------------------