Merging Compustat Annual with CRSP monthly

[Indy van Heijst]

Hello,

For my master thesis, I need to merge two datasets.
The first "master" file is a compustat annual dataset, containing variables: IB, oancf, Xidoc, sale, csho, prcc_f, gvkey, conm, tic, fyr, sic, and Cusip.
The second dataset is a CRSP monthly dataset, containing monthly returns, and vwretd, and the identifiers: Cusip, permno and permco.

For a long period of time, I am trying to merge the datasets with the common identifier CUSIP.
Since Compustat contains a 9-digit CUSIP and CRSP an 8-digit Cusip, I firstly generated an 8 digit cusip by:
Gen Cusip_8 = substr(Cusip,1,8)

Afterwards, after sorting the datasets by Cusip_8 and fyear, I tried to merge the master file with the monthly CRSP dataset:
sort cusip fyear
describe
merge 1:m cusip fyear using "link of CRSP dataset.dta"

However, whatever I try to do, I always get the error:
"variables Cusip_8 fyear do not uniquely identify observations in the master data"

Could someone maybe help me, or explain another way on how to merge the two datasets?
Thanks in advance!


Example Datasets:

Compustat Annual dataset:
* Example generated by -dataex-. For more info, type help dataex
clear
input str6 gvkey long datadate double fyear str12 indfmt str2(consol popsrc) str12 datafmt str8 tic str10 cusip str70 conm str4 curcd double(fyr csho ib oancf sale xidoc) str2 costat double prcc_f str4 sic str8 Cusip_8
"001003" 10257 1987 "INDL" "C" "D" "STD" "ANTQ" "000354100" "A.A. IMPORTING CO INC" "USD" 1 2.683 -.525 -.987 37.356 .711 "I" 2.75 "5712" "00035410"
"001003" 10623 1988 "INDL" "C" "D" "STD" "ANTQ" "000354100" "A.A. IMPORTING CO INC" "USD" 1 2.683 -7.838 -2.1 32.808 0 "I" 1.75 "5712" "00035410"
"001003" 10988 1989 "INDL" "C" "D" "STD" "ANTQ" "000354100" "A.A. IMPORTING CO INC" "USD" 1 2.683 -2.554 -.032 19.267 2.333 "I" .125 "5712" "00035410"
"001004" 10378 1987 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.87 21.233 . 347.64 0 "A" 25.12497711 "5080" "00036110"
"001004" 10743 1988 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 16.009 24.814 .094 406.36 0 "A" 31.24999237 "5080" "00036110"
"001004" 11108 1989 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 16.082 25.655 19.371 444.875 0 "A" 21.24999762 "5080" "00036110"
"001004" 11473 1990 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.891 14.801 36.891 466.542 0 "A" 14.12499905 "5080" "00036110"
"001004" 11839 1991 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.899 10.02 8.814 422.657 0 "A" 12.87499809 "5080" "00036110"
"001004" 12204 1992 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.901 .283 16.806 382.78 0 "A" 13.49999857 "5080" "00036110"
"001004" 12569 1993 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.906 9.484 6.697 407.754 0 "A" 14.37499809 "5080" "00036110"
"001004" 12934 1994 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.961 10.463 15.255 451.395 0 "A" 15.24999905 "5080" "00036110"
"001004" 13300 1995 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 15.998 16.012 24.76 504.99 0 "A" 22.12499857 "5080" "00036110"
"001004" 13665 1996 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 18.204 23.025 9.531 589.328 0 "A" 30.99998474 "5080" "00036110"
"001004" 14030 1997 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 27.704 35.657 22.823 782.123 0 "A" 26.4375 "5080" "00036110"
"001004" 14395 1998 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 27.381 41.671 28.525 918.036 0 "A" 19.75 "5080" "00036110"
"001004" 14761 1999 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 26.865 35.163 10.051 1024.333 0 "A" 13.875 "5080" "00036110"
"001004" 15126 2000 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 26.937 18.531 46.093 874.255 0 "A" 14 "5080" "00036110"
"001004" 15491 2001 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 31.87 -58.939 -33.315 638.721 0 "A" 11.44 "5080" "00036110"
"001004" 15856 2002 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 31.851 -12.41 34.733 606.337 0 "A" 4.5 "5080" "00036110"
"001004" 16222 2003 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 32.245 3.504 14.572 651.958 0 "A" 9.58 "5080" "00036110"
"001004" 16587 2004 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 32.586 18.572 50.938 747.848 -3.119 "A" 16.04 "5080" "00036110"
"001004" 16952 2005 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 36.654 35.163 -40.482 897.284 0 "A" 24.08 "5080" "00036110"
"001004" 17317 2006 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 37.729 59.447 -21.239 1061.169 -.787 "A" 32.5 "5080" "00036110"
"001004" 17683 2007 "INDL" "C" "D" "STD" "AIR" "000361105" "AAR CORP" "USD" 5 38.773 75.745 16.926 1384.919 -.601 "A" 19.28 "5080" "00036110"
"001009" 10165 1987 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 .842 .848 . 19.55 .312 "I" 11.99997711 "3460" "00078110"
"001009" 10531 1988 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 .842 1.266 1.654 28.419 .239 "I" 13.99998093 "3460" "00078110"
"001009" 10896 1989 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 2.526 1.317 2.226 36.386 .647 "I" 6.99999809 "3460" "00078110"
"001009" 11261 1990 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 2.526 1.431 2.075 40.522 .704 "I" 5.99999809 "3460" "00078110"
"001009" 11626 1991 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 2.526 .857 3.379 36.222 .227 "I" 9.99999809 "3460" "00078110"
"001009" 11992 1992 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 2.526 2.388 6.024 51.407 0 "I" 14.24998856 "3460" "00078110"
"001009" 12357 1993 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 5.052 3.362 3.447 72.36 0 "I" 12.75 "3460" "00078110"
"001009" 12722 1994 "INDL" "C" "D" "STD" "ABSI.1" "000781104" "ABS INDUSTRIES INC" "USD" 10 5.052 4.523 1.925 92.122 .332 "I" 13.75 "3460" "00078110"
"001010" 10226 1987 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 5.28 . 233.626 0 "I" . "3743" "00099V00"
"001010" 10592 1988 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 15.062 -34.373 287.723 0 "I" . "3743" "00099V00"
"001010" 10957 1989 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 283.886 100.832 326.45 0 "I" . "3743" "00099V00"
"001010" 11322 1990 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 -84.21 28.377 312.309 -4.597 "I" . "3743" "00099V00"
"001010" 11687 1991 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 156.959 48.569 304.091 0 "I" . "3743" "00099V00"
"001010" 12053 1992 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 -19.781 62.208 320.148 1.971 "I" . "3743" "00099V00"
"001010" 12418 1993 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 127.441 8.705 348.429 -7.856 "I" . "3743" "00099V00"
"001010" 12783 1994 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 25.2 36.2 380.5 0 "I" . "3743" "00099V00"
"001010" 13148 1995 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 84.3 86.7 407.2 0 "I" . "3743" "00099V00"
"001010" 13514 1996 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 92.4 80 486.8 0 "I" . "3743" "00099V00"
"001010" 13879 1997 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 237.9 90.9 501.9 13.2 "I" . "3743" "00099V00"
"001010" 14244 1998 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 67.2 92.4 536.5 0 "I" . "3743" "00099V00"
"001010" 14609 1999 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 77.3 67.5 472.4 0 "I" . "3743" "00099V00"
"001010" 14975 2000 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .015 79.9 37.1 443.8 0 "I" . "3743" "00099V00"
"001010" 15340 2001 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .001 145.7 114.2 366.5 0 "I" . "3743" "00099V00"
"001010" 15705 2002 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 .001 79.7 165.3 313.3 0 "I" . "3743" "00099V00"
"001010" 16070 2003 "INDL" "C" "D" "STD" "4165A" "00099V004" "ACF INDUSTRIES INC" "USD" 12 . 344.2 -45.7 2339.1 -40.7 "I" . "3743" "00099V00"
"001011" 10226 1987 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 3.299 -.126 . 2.721 -.793 "I" .438 "4841" "00087230"
"001011" 10592 1988 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 3.299 .292 .695 2.589 .01 "I" 1.5 "4841" "00087230"
"001011" 10957 1989 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 3.549 -.788 -.525 3.287 0 "I" 2 "4841" "00087230"
"001011" 11322 1990 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 3.556 -1.869 -.781 3.635 0 "I" 1.188 "4841" "00087230"
"001011" 11687 1991 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 3.566 -1.448 -.243 4.465 0 "I" 1.5 "4841" "00087230"
"001011" 12053 1992 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 1.745 -2.153 -.941 4.664 0 "I" 11.25 "4841" "00087230"
"001011" 12418 1993 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 6.957 -3.158 -.817 6.49 0 "I" 15 "4841" "00087230"
"001011" 12783 1994 "INDL" "C" "D" "STD" "ACSE" "000872309" "ACS ENTERPRISES INC" "USD" 12 10.425 -9.198 2.719 17.739 0 "I" 8.75 "4841" "00087230"
"001012" 10165 1987 "INDL" "C" "D" "STD" "6927B" "000874107" "ACS INDUSTRIES INC" "USD" 10 1.188 -.147 . 27.434 0 "I" 3.75 "3357" "00087410"
"001012" 10531 1988 "INDL" "C" "D" "STD" "6927B" "000874107" "ACS INDUSTRIES INC" "USD" 10 1.188 -.181 1.866 35.041 0 "I" 3.75 "3357" "00087410"
"001012" 10896 1989 "INDL" "C" "D" "STD" "6927B" "000874107" "ACS INDUSTRIES INC" "USD" 10 1.188 .917 2.735 45.091 0 "I" 5 "3357" "00087410"
"001013" 10165 1987 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 12.973 15.263 . 166.863 0 "I" 16 "3661" "00088630"
"001013" 10531 1988 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 13.104 16.953 26.596 179.852 0 "I" 11.625 "3661" "00088630"
"001013" 10896 1989 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 13.218 16.403 17.9 196.388 0 "I" 15.375 "3661" "00088630"
"001013" 11261 1990 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 13.289 22.903 34.695 259.802 0 "I" 16.375 "3661" "00088630"
"001013" 11626 1991 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 13.429 22.025 36.703 293.839 0 "I" 24.375 "3661" "00088630"
"001013" 11992 1992 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 13.61 21.026 34.755 316.496 0 "I" 36.25 "3661" "00088630"
"001013" 12357 1993 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 27.697 31.636 29.448 366.118 0 "I" 36.5 "3661" "00088630"
"001013" 12722 1994 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 27.888 40.521 58.201 448.735 -1.45 "I" 47.125 "3661" "00088630"
"001013" 13087 1995 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 62.737 55.186 44.259 586.222 0 "I" 40 "3661" "00088630"
"001013" 13453 1996 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 65.177 87.463 63.457 828.009 0 "I" 68.375 "3661" "00088630"
"001013" 13818 1997 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 133.508 108.837 79.713 1164.45 0 "I" 33.125 "3661" "00088630"
"001013" 14183 1998 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 134.897 146.727 82.078 1379.678 0 "I" 23 "3661" "00088630"
"001013" 14548 1999 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 150.173 87.635 332.281 1926.947 0 "I" 47.6875 "3661" "00088630"
"001013" 14914 2000 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 770.3 868.1 221.4 3287.9 0 "I" 21.375 "3661" "00088630"
"001013" 15279 2001 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 792 -1287.7 95 2402.8 0 "I" 4.55 "3661" "00088630"
"001013" 15644 2002 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 799.6 -1145 60.5 1047.7 0 "I" 1.58 "3661" "00088630"
"001013" 16009 2003 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 806.6 -76.7 38.9 773.2 0 "I" 2.57 "3661" "00088630"
"001013" 16375 2004 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 810.1 31.3 3.1 784.3 -69.3 "I" 2.21 "3661" "00088630"
"001013" 16740 2005 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 116.5 85.5 58.6 1169.2 -1.4 "I" 17.45 "3661" "00088630"
"001013" 17105 2006 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 117.2 94.2 87.1 1281.9 -6.4 "I" 14.31 "3661" "00088630"
"001013" 17470 2007 "INDL" "C" "D" "STD" "ADCT.1" "000886309" "ADC TELECOMMUNICATIONS INC" "USD" 10 117.6 113.3 141.8 1322.2 -10.7 "I" 18.7 "3661" "00088630"
"001014" 10042 1987 "INDL" "C" "D" "STD" "3ADDS" "000887109" "ADDSCO INDUSTRIES INC" "USD" 6 .685 -.349 . 54.527 0 "I" 14.5 "6512" "00088710"
"001014" 10408 1988 "INDL" "C" "D" "STD" "3ADDS" "000887109" "ADDSCO INDUSTRIES INC" "USD" 6 .685 -5.868 -.709 37.39 1.293 "I" . "6512" "00088710"
"001014" 10773 1989 "INDL" "C" "D" "STD" "3ADDS" "000887109" "ADDSCO INDUSTRIES INC" "USD" 6 .685 1.433 4.786 2.312 -8.994 "I" 10.25 "6512" "00088710"
"001014" 11138 1990 "INDL" "C" "D" "STD" "3ADDS" "000887109" "ADDSCO INDUSTRIES INC" "USD" 6 .685 2.705 .677 2.644 -.456 "I" 11 "6512" "00088710"
"001014" 11503 1991 "INDL" "C" "D" "STD" "3ADDS" "000887109" "ADDSCO INDUSTRIES INC" "USD" 6 .685 1.998 3.376 4.057 1.721 "I" 14.5 "6512" "00088710"
"001014" 11869 1992 "INDL" "C" "D" "STD" "3ADDS" "000887109" "ADDSCO INDUSTRIES INC" "USD" 6 .675 1.591 .791 3.28 -.4 "I" 16 "6512" "00088710"
"001015" 10073 1987 "INDL" "C" "D" "STD" "4327B" "000893107" "ADI ELECTRONICS INC" "USD" 7 3.736 -9.198 . 4.187 0 "I" .875 "3678" "00089310"
"001016" 10165 1987 "INDL" "C" "D" "STD" "AECE" "001015106" "AEC INC" "USD" 10 1.654 -2.334 . 65.899 0 "I" 8 "3585" "00101510"
"001017" 10286 1987 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.971 2.126 2.665 119.637 0 "I" 9.5 "3812" "00103010"
"001017" 10651 1988 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.91 -1.984 -7.956 136.997 0 "I" 8 "3812" "00103010"
"001017" 11016 1989 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.892 -8.987 12.443 121.159 0 "I" 5.25 "3812" "00103010"
"001017" 11381 1990 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.882 1.722 9.994 144.258 .852 "I" 5.125 "3812" "00103010"
"001017" 11747 1991 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.883 10.456 12.248 140.112 1.846 "I" 8 "3812" "00103010"
"001017" 12112 1992 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.741 -2.056 3.055 113.5 0 "I" 6.5 "3812" "00103010"
"001017" 12477 1993 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.768 1.617 8.816 124.13 0 "I" 8.375 "3812" "00103010"
"001017" 12842 1994 "INDL" "C" "D" "STD" "AELNA" "001030105" "AEL INDUSTRIES -CL A" "USD" 2 3.804 1.769 1.825 126.78 0 "I" 16.25 "3812" "00103010"
"001018" 10042 1987 "INDL" "C" "D" "STD" "2938B" "001032101" "AES TECHNOLOGY SYSTEMS INC" "USD" 6 6.58 -.84 . 4.131 0 "I" .062 "3861" "00103210"
"001019" 10226 1987 "INDL" "C" "D" "STD" "AFAP" "001038108" "AFA PROTECTIVE SYSTEMS INC" "USD" 12 .236 .913 . 18.38 0 "I" 64 "7380" "00103810"
"001019" 10592 1988 "INDL" "C" "D" "STD" "AFAP" "001038108" "AFA PROTECTIVE SYSTEMS INC" "USD" 12 .231 1.789 4.647 20.59 0 "I" 64 "7380" "00103810"
end
format %td datadate
[/CODE]


CRSP monthly:

* Example generated by -dataex-. For more info, type help dataex
clear
input double PERMNO long date double SICCD str8 TICKER str36 COMNAM str8 NAICS double PERMCO str8 CUSIP double(RET vwretd) str8 Cusip_8
10000 9891 3990 "OMFGA" "OPTIMUM MANUFACTURING INC" "" 7952 "68391610" -.21212121844291687 .1284987 "68391610"
10000 9919 3990 "OMFGA" "OPTIMUM MANUFACTURING INC" "" 7952 "68391610" 0 .047921820000000004 "68391610"
10000 9951 3990 "OMFGA" "OPTIMUM MANUFACTURING INC" "" 7952 "68391610" -.38461539149284363 .02366445 "68391610"
10000 9981 3990 "OMFGA" "OPTIMUM MANUFACTURING INC" "" 7952 "68391610" -.0625 -.01699554 "68391610"
10000 10010 3990 "OMFGA" "OPTIMUM MANUFACTURING INC" "" 7952 "68391610" -.06666667014360428 .005122664000000001 "68391610"
10000 10042 3990 "OMFGA" "OPTIMUM MANUFACTURING INC" "" 7952 "68391610" . .04365455 "68391610"
10001 9891 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.0357142873108387 .1284987 "36720410"
10001 9919 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.07407407462596893 .047921820000000004 "36720410"
10001 9951 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .03680000081658363 .02366445 "36720410"
10001 9981 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.03921568766236305 -.01699554 "36720410"
10001 10010 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.0714285746216774 .005122664000000001 "36720410"
10001 10042 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .051428571343421936 .04365455 "36720410"
10001 10073 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .021276595070958138 .04424724 "36720410"
10001 10104 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .0833333358168602 .0371465 "36720410"
10001 10134 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.02230769209563732 -.02077283 "36720410"
10001 10164 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .019999999552965164 -.2253613 "36720410"
10001 10195 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.029411764815449715 -.07227181 "36720410"
10001 10226 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.03353535383939743 .07032388 "36720410"
10001 10255 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .06382978707551956 .04487472 "36720410"
10001 10286 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .07999999821186066 .051691270000000004 "36720410"
10001 10317 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.07629629969596863 -.01659768 "36720410"
10001 10346 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .030612245202064514 .01099253 "36720410"
10001 10378 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .019801979884505272 .0004473087 "36720410"
10001 10408 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.01203883532434702 .05145697 "36720410"
10001 10437 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .029999999329447746 -.007272285000000001 "36720410"
10001 10470 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .029126213863492012 -.02800578 "36720410"
10001 10500 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.021132076159119606 .03720373 "36720410"
10001 10531 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .03921568766236305 .01764535 "36720410"
10001 10561 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" 0 -.01641086 "36720410"
10001 10591 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.021132076159119606 .02107066 "36720410"
10001 10623 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .019607843831181526 .06610128 "36720410"
10001 10651 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .03846153989434242 -.01644182 "36720410"
10001 10682 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .017777778208255768 .02146452 "36720410"
10001 10710 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .07407407462596893 .04820698 "36720410"
10001 10743 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.03448275849223137 .03933567 "36720410"
10001 10773 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .017142856493592262 -.004855535 "36720410"
10001 10804 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .0357142873108387 .07712836 "36720410"
10001 10835 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .27586206793785095 .022126 "36720410"
10001 10864 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.027027027681469917 -.0014733320000000002 "36720410"
10001 10896 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .07042253762483597 -.02928516 "36720410"
10001 10926 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .03947368264198303 .01781615 "36720410"
10001 10955 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .037974681705236435 .01829401 "36720410"
10001 10988 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.018518518656492233 -.07011361 "36720410"
10001 11016 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.006289307959377766 .01489994 "36720410"
10001 11046 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .012658228166401386 .02414776 "36720410"
10001 11077 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" 0 -.028283060000000002 "36720410"
10001 11108 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.012658228166401386 .0889347 "36720410"
10001 11137 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .014102564193308353 -.004192862 "36720410"
10001 11169 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .025641025975346565 -.009391909 "36720410"
10001 11200 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.05000000074505806 -.0919028 "36720410"
10001 11228 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .04078947380185127 -.05384421 "36720410"
10001 11261 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.012820512987673283 -.01249875 "36720410"
10001 11291 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" 0 .06574162 "36720410"
10001 11322 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .00129870162345469 .02951084 "36720410"
10001 11353 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .01315789483487606 .04908338 "36720410"
10001 11381 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .012987012974917889 .07584751 "36720410"
10001 11409 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.011538460850715637 .02892205 "36720410"
10001 11442 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .03947368264198303 .0033108020000000003 "36720410"
10001 11473 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" 0 .04073652 "36720410"
10001 11501 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .07848101109266281 -.04402354 "36720410"
10001 11534 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.0357142873108387 .04677859 "36720410"
10001 11564 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .1358024626970291 .026806780000000002 "36720410"
10001 11595 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .013043479062616825 -.01097861 "36720410"
10001 11626 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .1304347813129425 .017847000000000002 "36720410"
10001 11655 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .13461539149284363 -.03729085 "36720410"
10001 11687 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.0067796604707837105 .1067822 "36720410"
10001 11718 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.0517241396009922 -.0011635480000000001 "36720410"
10001 11746 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.20000000298023224 .013355210000000001 "36720410"
10001 11778 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .08181818574666977 -.02369942 "36720410"
10001 11808 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .010638297535479069 .01341432 "36720410"
10001 11837 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .010526316240429878 .006407138000000001 "36720410"
10001 11869 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.007708333432674408 -.0192581 "36720410"
10001 11900 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .06382978707551956 .03989972 "36720410"
10001 11931 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .03999999910593033 -.02081892 "36720410"
10001 11961 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .16596153378486633 .01246087 "36720410"
10001 11991 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.02500000037252903 .01098284 "36720410"
10001 12022 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.017094017937779427 .04018138 "36720410"
10001 12053 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.01513043511658907 .01773988 "36720410"
10001 12082 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" 0 .012615610000000001 "36720410"
10001 12110 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .01785714365541935 .005425406000000001 "36720410"
10001 12143 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .0110526317730546 .02508918 "36720410"
10001 12173 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .07017543911933899 -.02539078 "36720410"
10001 12201 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.008196720853447914 .02957208 "36720410"
10001 12234 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .10247933864593506 .005434345 "36720410"
10001 12264 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.007575757801532745 -.0008060529 "36720410"
10001 12296 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" -.030534351244568825 .03949608 "36720410"
10001 12326 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .06614173203706741 .0006287303 "36720410"
10001 12355 4920 "GFGC" "GREAT FALLS GAS CO" "" 7953 "36720410" .02985074557363987 .01805087 "36720410"
10001 12387 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" -.014492753893136978 -.017600460000000002 "36720410"
10001 12418 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" .09117647260427475 .01955422 "36720410"
10001 12449 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" -.0476190485060215 .03145912 "36720410"
10001 12477 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" 0 -.024206850000000002 "36720410"
10001 12508 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" -.004285714589059353 -.04579461 "36720410"
10001 12537 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" -.14492753148078918 .009494642000000001 "36720410"
10001 12569 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" .06779661029577255 .009352694 "36720410"
10001 12599 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" .10730158537626266 -.02788023 "36720410"
10001 12628 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" .07246376574039459 .03065685 "36720410"
10001 12661 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" -.027027027681469917 .04262911 "36720410"
10001 12691 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" .038333334028720856 -.01833769 "36720410"
10001 12722 4920 "EWST" "ENERGY WEST INC" "" 7953 "36720410" -.054054055362939835 .01452095 "36720410"
end
format %td date
[/CODE]

[Clyde Schechter]

Your example data does not reproduce this problem, so it is not possible to give specific advice.

Generically, the problem is precisely what the message says. In order to do a 1:m merge, it must be the case that the merge key variables (Cusip_8 and fyear) together uniquely identify observations in the Compustat data. Stata is telling you that they don't, and I have never known Stata to be wrong about this kind of thing. So, somewhere in your Compustat data set, there is at least one combination of Cusip_8 and fyear that appears more than once. There may be many such. In any case, to find them, do this:

duplicates tag Cusip_8 fyear, gen(flag)
browse if flag

You will then have to figure out why those duplicates are there and how to eliminate them. One possibility suggests itself in your specific circumstance: it may be that the original 9-digit Cusip variable and fyear uniquely identify observations, but when you chop off that 9th digit there are two distinct 9-digit Cusips that become the same 8-digit Cusip. Or it may just be that there are sporadic surplus observations in the data. In any case, you will have to look at what you find and figure out how the data got to be that way. Usually it represents some error in the data management that created the data set. Sometimes you will find that the problem already existed in the source data you received from your vendors. Ideally, whoever created the problem should fix it. In reality it may be left to you to find a way to fix the problem yourself.