求问，stata中用merge m:1 匹配后存在部分数据匹配错误是什么原因？如何解决？
面板数据，辅表是公司-年度数据（Year），主表是公司-月度数据（Month），要把年度数据merge到月度数据表格中，唯一标识是ID，为股票代码和年份（例如ID=“0000022009”），打开月度数据文件，stata代码如下

主表（Month）部分数据如下


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[CODE]
* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 Code str4 Year1 int t str10 ID double(RFt MVet)
"000002" "2009" 17928 "0000022009"             .010006  915.6069708564543
"000002" "2009" 17956 "0000022009"             .009605  1055.846662409969
"000002" "2009" 17987 "0000022009"              .00981 1364.0598223200764
"000002" "2009" 18017 "0000022009"             .016408  1421.957501604218
"000002" "2009" 18048 "0000022009"             .016023 1014.2458197351197
"000002" "2009" 18078 "0000022009"             .014455 1121.5360154185607
"000002" "2009" 18109 "0000022009" .015170999999999999 1226.2244715475588
"000002" "2009" 18140 "0000022009" .014820999999999999 1230.8107573852722
"000002" "2009" 18170 "0000022009" .014953000000000001 1159.0886991472096
"000002" "2009" 18201 "0000022009" .016529000000000002  995.2635567267103
"000002" "2009" 18231 "0000022009"             .016294  1008.700347360728
"000002" "2009" 18262 "0000022009" .015501000000000001  1022.635842809829
"000002" "2010" 18293 "0000022010"             .015892  842.3311966129778
"000002" "2010" 18321 "0000022010"             .018162  789.2383711195743
"000002" "2010" 18352 "0000022010" .021345999999999997  750.2731847096659
"000002" "2010" 18382 "0000022010"             .019318  918.9252458095446
"000002" "2010" 18413 "0000022010"             .019163  924.4181010429487
"000002" "2010" 18443 "0000022010"             .019459  924.5291320019117
"000002" "2010" 18474 "0000022010"              .02043 1065.1108630687625
"000002" "2010" 18505 "0000022010"             .027925  897.8020962345086
"000002" "2010" 18535 "0000022010"                .033  903.1347058629831
"000002" "2010" 18566 "0000022010"             .031527  901.3041669397354
"000002" "2010" 18596 "0000022010"                 .03  890.9692864018114
"000002" "2010" 18627 "0000022010" .028734000000000003  954.1813045531461
"000002" "2011" 18658 "0000022011"             .028094  941.8653192268572
"000002" "2011" 18686 "0000022011"             .030348  876.2309443781596
"000002" "2011" 18717 "0000022011"             .034742  932.5848606830472
"000002" "2011" 18747 "0000022011" .037339000000000004  905.8379363103577
"000002" "2011" 18778 "0000022011"             .039174   896.665858929964
"000002" "2011" 18808 "0000022011"             .036069   773.224047786045
"000002" "2011" 18839 "0000022011"             .031398  868.4465311005226
"000002" "2011" 18870 "0000022011"             .027366  762.7309496250799
"000002" "2011" 18900 "0000022011"             .027167  804.9864715843038
"000002" "2011" 18931 "0000022011" .027658000000000002  831.2659244129657
"000002" "2011" 18961 "0000022011" .029474999999999998   908.210060329776
"000002" "2011" 18992 "0000022011"             .028355  899.6983838293878
"000002" "2012" 19023 "0000022012" .028561999999999997  979.5264206812299
"000002" "2012" 19052 "0000022012"             .022307 1004.4180245119776


辅表（Year）部分数据如下
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[CODE]
* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 Code str4 Year str10 ID double Et
"000002" "2009" "0000022009"        46.3986915273
"000002" "2010" "0000022010"    64.30007538689999
"000002" "2011" "0000022011"    88.39610505040001
"000002" "2012" "0000022012"       115.9960621177
"000002" "2013" "0000022013"       156.6258842306
"000002" "2014" "0000022014"   182.97549871240003
"000002" "2015" "0000022015"   192.87524028080003
"000002" "2016" "0000022016"       259.4943802631
"000002" "2017" "0000022017"       283.5025548066
"000002" "2018" "0000022018"       372.0838733007
"000002" "2019" "0000022019"       492.7229453461
"000004" "2009" "0000042009"  -.11484191490000001
"000004" "2011" "0000042011"   .20201272920000002
"000004" "2012" "0000042012"          .0919306782
"000004" "2013" "0000042013"          .0781422529
"000004" "2014" "0000042014"          .0579674979
"000004" "2015" "0000042015"          .1562481356
"000004" "2016" "0000042016"   .06857151709999999
"000004" "2017" "0000042017"          .3971631622
"000004" "2018" "0000042018"          .0589224141
"000004" "2019" "0000042019"  -.21612682100000002
"000005" "2009" "0000052009"          .1049971992
"000005" "2010" "0000052010"         -.4891952898
"000005" "2011" "0000052011" -.044263870999999996
"000005" "2013" "0000052013"          .2202161789
"000005" "2014" "0000052014"  -.42344755219999997
"000005" "2015" "0000052015"   .43163944159999995
"000005" "2016" "0000052016"          -.540317165
"000005" "2017" "0000052017"         1.1696241987
"000005" "2018" "0000052018"          .2293599194
"000005" "2019" "0000052019"   1.5674862608000002
"000006" "2009" "0000062009"         1.5021106891
"000006" "2010" "0000062010"   3.3522296907999998
"000006" "2011" "0000062011"         4.9646507546
"000006" "2012" "0000062012"         4.3411700789
"000006" "2013" "0000062013"         6.2956537996
"000006" "2014" "0000062014"           6.98009106
"000006" "2015" "0000062015"         5.1245355951
"000006" "2016" "0000062016"         4.3878591509
"000006" "2017" "0000062017"         8.0387652551
"000006" "2019" "0000062019"         9.2312739615
"000007" "2009" "0000072009"         -.6500725877
"000007" "2010" "0000072010"   .20420709850000002
"000007" "2011" "0000072011"          .2170015805
"000007" "2012" "0000072012"          .0831053862
"000007" "2013" "0000072013"  .044332963899999994
"000007" "2014" "0000072014"          .1883060346
"000007" "2015" "0000072015"         -.3338264702
"000007" "2016" "0000072016"          .1323887222
"000007" "2017" "0000072017"           .815679611
"000007" "2019" "0000072019"  -1.9620020149000001
"000008" "2009" "0000082009" .0074803714000000006
"000008" "2010" "0000082010"          .0031348874
"000008" "2011" "0000082011"          .0088894826
"000008" "2012" "0000082012" -.005394518199999999
"000008" "2013" "0000082013"          .3912903059
"000008" "2014" "0000082014"          .2275795394
"000008" "2015" "0000082015"          .0776640264
"000008" "2016" "0000082016"   1.8990915959999999
"000008" "2017" "0000082017"         5.3054164136
"000008" "2018" "0000082018"         8.8960989013
"000008" "2019" "0000082019"         3.4188969813
"000009" "2009" "0000092009"   2.7154491923000004
"000009" "2010" "0000092010"         4.0859440942
"000009" "2011" "0000092011"         4.4159406586
"000009" "2012" "0000092012"   3.8043540827999998
"000009" "2013" "0000092013"         3.0730112667
合并后部分数据如下，含有部分匹配错误，变成重复值的数据（从"0000022011"开始往下Et都是错误数据，第二、三行的RFt、第四、五、八、九、十行的MVet等等也都是错误数据）

----------------------- copy starting from the next line -----------------------
[CODE]
* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 Code2 str4 Year1 int t str10 ID double(Et RFt MVet)
"000002" "2009" 17928 "0000022009"     46.3986915273             .010006  915.6069708564543
"000002" "2009" 17956 "0000022009"     46.3986915273             .010006  1055.846662409969
"000002" "2009" 17987 "0000022009"     46.3986915273             .010006             1125.3
"000002" "2009" 18017 "0000022009"     46.3986915273             .016408             1125.3
"000002" "2009" 18048 "0000022009"     46.3986915273             .016023 1014.2458197351197
"000002" "2009" 18078 "0000022009"     46.3986915273             .014455 1121.5360154185607
"000002" "2009" 18109 "0000022009"     46.3986915273 .015170999999999999             1125.3
"000002" "2009" 18140 "0000022009"     46.3986915273 .014820999999999999             1125.3
"000002" "2009" 18170 "0000022009"     46.3986915273 .014953000000000001             1125.3
"000002" "2009" 18201 "0000022009"     46.3986915273 .016529000000000002  995.2635567267103
"000002" "2009" 18231 "0000022009"     46.3986915273             .016294  1008.700347360728
"000002" "2009" 18262 "0000022009"     46.3986915273 .015501000000000001  1022.635842809829
"000002" "2010" 18293 "0000022010" 64.30007538689999             .015892  842.3311966129778
"000002" "2010" 18321 "0000022010" 64.30007538689999             .018162  789.2383711195743
"000002" "2010" 18352 "0000022010" 64.30007538689999 .021345999999999997  750.2731847096659
"000002" "2010" 18382 "0000022010" 64.30007538689999             .019318  918.9252458095446
"000002" "2010" 18413 "0000022010" 64.30007538689999             .019163  924.4181010429487
"000002" "2010" 18443 "0000022010" 64.30007538689999             .019459  924.5291320019117
"000002" "2010" 18474 "0000022010" 64.30007538689999              .02043 1065.1108630687625
"000002" "2010" 18505 "0000022010" 64.30007538689999             .027925  897.8020962345086
"000002" "2010" 18535 "0000022010" 64.30007538689999                .033  903.1347058629831
"000002" "2010" 18566 "0000022010" 64.30007538689999             .031527  901.3041669397354
"000002" "2010" 18596 "0000022010" 64.30007538689999                 .03  890.9692864018114
"000002" "2010" 18627 "0000022010" 64.30007538689999 .028734000000000003  954.1813045531461
"000002" "2011" 18658 "0000022011"       78.60411559             .028094  941.8653192268572
"000002" "2011" 18686 "0000022011"       78.60411559             .030348  876.2309443781596
"000002" "2011" 18717 "0000022011"       78.60411559             .034742  932.5848606830472
"000002" "2011" 18747 "0000022011"       78.60411559 .037339000000000004  905.8379363103577
"000002" "2011" 18778 "0000022011"       78.60411559             .039174   896.665858929964
"000002" "2011" 18808 "0000022011"       78.60411559             .036069   773.224047786045
"000002" "2011" 18839 "0000022011"       78.60411559             .031398  868.4465311005226
"000002" "2011" 18870 "0000022011"       78.60411559             .027366  762.7309496250799
"000002" "2011" 18900 "0000022011"       78.60411559             .027167  804.9864715843038
"000002" "2011" 18931 "0000022011"       78.60411559 .027658000000000002  831.2659244129657
"000002" "2011" 18961 "0000022011"       78.60411559 .029474999999999998   908.210060329776
"000002" "2011" 18992 "0000022011"       78.60411559             .028355  899.6983838293878
"000002" "2012" 19023 "0000022012"       78.60411559 .028561999999999997  979.5264206812299
"000002" "2012" 19052 "0000022012"       78.60411559             .022307 1004.4180245119776
"000002" "2012" 19083 "0000022012"       78.60411559              .02342  971.4236626818927
"000002" "2012" 19113 "0000022012"       78.60411559             .023077 1000.5302180347118
"000002" "2012" 19144 "0000022012"       78.60411559             .026806    880.69671403434
"000002" "2012" 19174 "0000022012"       78.60411559             .027921  920.8966713068766
"000002" "2012" 19205 "0000022012"       78.60411559 .029327000000000002  913.4670746436292
"000002" "2012" 19236 "0000022012"       78.60411559             .028834  975.0726540988401
"000002" "2012" 19266 "0000022012"       78.60411559              .02905  1112.955437333475
"000002" "2012" 19297 "0000022012"       78.60411559             .028047             1125.3
"000002" "2012" 19327 "0000022012"       78.60411559             .027612             1125.3
"000002" "2012" 19358 "0000022012"       78.60411559 .026789999999999998             1125.3
"000002" "2013" 19389 "0000022013"       78.60411559             .027842             1125.3
"000002" "2013" 19417 "0000022013"       78.60411559             .028682             1125.3
"000002" "2013" 19448 "0000022013"       78.60411559 .034811999999999996 1100.3169535854206
"000002" "2013" 19478 "0000022013"       78.60411559             .034908 1071.0416926807593
"000002" "2013" 19509 "0000022013"       78.60411559 .036185999999999996  1080.935173125802
"000002" "2013" 19539 "0000022013"       78.60411559             .035451 1033.5457327137774


谢谢各位大神