Dear Members
I have some doubts which I will illustrate with a sample dataset




Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input str5 ric int year str28 companyname byte industry
"ONE.V" 1999 "01 Communique Laboratory Inc" .
"ONE.V" 1999 "01 Communique Laboratory Inc" .
"ONE.V" 2000 "01 Communique Laboratory Inc" .
"ONE.V" 2000 "01 Communique Laboratory Inc" .
"ONE.V" 2001 "01 Communique Laboratory Inc" .
"ONE.V" 2001 "01 Communique Laboratory Inc" .
"ONE.V" 2002 "01 Communique Laboratory Inc" .
"ONE.V" 2002 "01 Communique Laboratory Inc" .
"ONE.V" 2003 "01 Communique Laboratory Inc" .
"ONE.V" 2003 "01 Communique Laboratory Inc" .
"ONE.V" 2004 "01 Communique Laboratory Inc" .
"ONE.V" 2004 "01 Communique Laboratory Inc" .
"ONE.V" 2005 "01 Communique Laboratory Inc" .
"ONE.V" 2005 "01 Communique Laboratory Inc" .
"ONE.V" 2006 "01 Communique Laboratory Inc" .
"ONE.V" 2006 "01 Communique Laboratory Inc" .
"ONE.V" 2007 "01 Communique Laboratory Inc" .
"ONE.V" 2007 "01 Communique Laboratory Inc" .
"ONE.V" 2008 "01 Communique Laboratory Inc" .
"ONE.V" 2008 "01 Communique Laboratory Inc" .
"ONE.V" 2009 "01 Communique Laboratory Inc" .
"ONE.V" 2009 "01 Communique Laboratory Inc" .
"ONE.V" 2010 "01 Communique Laboratory Inc" .
"ONE.V" 2010 "01 Communique Laboratory Inc" .
"ONE.V" 2011 "01 Communique Laboratory Inc" .
"ONE.V" 2011 "01 Communique Laboratory Inc" .
"ONE.V" 2012 "01 Communique Laboratory Inc" .
"ONE.V" 2012 "01 Communique Laboratory Inc" .
"ONE.V" 2013 "01 Communique Laboratory Inc" .
"ONE.V" 2013 "01 Communique Laboratory Inc" .
"ONE.V" 2014 "01 Communique Laboratory Inc" .
"ONE.V" 2014 "01 Communique Laboratory Inc" .
"ONE.V" 2015 "01 Communique Laboratory Inc" .
"ONE.V" 2015 "01 Communique Laboratory Inc" .
"ONE.V" 2016 "01 Communique Laboratory Inc" .
"ONE.V" 2016 "01 Communique Laboratory Inc" .
"ONE.V" 2017 "01 Communique Laboratory Inc" .
"ONE.V" 2017 "01 Communique Laboratory Inc" .
"ONE.V" 2018 "01 Communique Laboratory Inc" .
"ONE.V" 2018 "01 Communique Laboratory Inc" .
"ONE.V" 2019 "01 Communique Laboratory Inc" .
"ONE.V" 2019 "01 Communique Laboratory Inc" .
"ONE.V" 2020 "01 Communique Laboratory Inc" .
"ONE.V" 2020 "01 Communique Laboratory Inc" .
"A.V"   1999 "Armor Minerals Inc"           .
"A.V"   1999 "Armor Minerals Inc"           .
"A.V"   2000 "Armor Minerals Inc"           .
"A.V"   2000 "Armor Minerals Inc"           .
"A.V"   2001 "Armor Minerals Inc"           .
"A.V"   2001 "Armor Minerals Inc"           .
"A.V"   2002 "Armor Minerals Inc"           .
"A.V"   2002 "Armor Minerals Inc"           .
"A.V"   2003 "Armor Minerals Inc"           .
"A.V"   2003 "Armor Minerals Inc"           .
"A.V"   2004 "Armor Minerals Inc"           .
"A.V"   2004 "Armor Minerals Inc"           .
"A.V"   2005 "Armor Minerals Inc"           .
"A.V"   2005 "Armor Minerals Inc"           .
"A.V"   2006 "Armor Minerals Inc"           .
"A.V"   2006 "Armor Minerals Inc"           .
"A.V"   2007 "Armor Minerals Inc"           .
"A.V"   2007 "Armor Minerals Inc"           .
"A.V"   2008 "Armor Minerals Inc"           .
"A.V"   2008 "Armor Minerals Inc"           .
"A.V"   2009 "Armor Minerals Inc"           .
"A.V"   2009 "Armor Minerals Inc"           .
"A.V"   2010 "Armor Minerals Inc"           .
"A.V"   2010 "Armor Minerals Inc"           .
"A.V"   2011 "Armor Minerals Inc"           .
"A.V"   2011 "Armor Minerals Inc"           .
"A.V"   2012 "Armor Minerals Inc"           .
"A.V"   2012 "Armor Minerals Inc"           .
"A.V"   2013 "Armor Minerals Inc"           .
"A.V"   2013 "Armor Minerals Inc"           .
"A.V"   2014 "Armor Minerals Inc"           .
"A.V"   2014 "Armor Minerals Inc"           .
"A.V"   2015 "Armor Minerals Inc"           .
"A.V"   2015 "Armor Minerals Inc"           .
"A.V"   2016 "Armor Minerals Inc"           .
"A.V"   2016 "Armor Minerals Inc"           .
"A.V"   2017 "Armor Minerals Inc"           .
"A.V"   2017 "Armor Minerals Inc"           .
"A.V"   2018 "Armor Minerals Inc"           .
"A.V"   2018 "Armor Minerals Inc"           .
"A.V"   2019 "Armor Minerals Inc"           .
"A.V"   2019 "Armor Minerals Inc"           .
"A.V"   2020 "Armor Minerals Inc"           .
"A.V"   2020 "Armor Minerals Inc"           .
"RP.V"  1999 "Replicel Life Sciences Inc"   .
"Rp.V"  1999 "Replicel Life Sciences Inc"   .
"Rp.V"  1999 "Replicel Life Sciences Inc"   .
"RP.V"  2000 "Replicel Life Sciences Inc"   .
"Rp.V"  2000 "Replicel Life Sciences Inc"   .
"Rp.V"  2000 "Replicel Life Sciences Inc"   .
"Rp.V"  2001 "Replicel Life Sciences Inc"   .
"Rp.V"  2001 "Replicel Life Sciences Inc"   .
"RP.V"  2001 "Replicel Life Sciences Inc"   .
"Rp.V"  2002 "Replicel Life Sciences Inc"   .
"RP.V"  2002 "Replicel Life Sciences Inc"   .
"Rp.V"  2002 "Replicel Life Sciences Inc"   .
"Rp.V"  2003 "Replicel Life Sciences Inc"   .
"RP.V"  2003 "Replicel Life Sciences Inc"   .
"Rp.V"  2003 "Replicel Life Sciences Inc"   .
"Rp.V"  2004 "Replicel Life Sciences Inc"   .
"Rp.V"  2004 "Replicel Life Sciences Inc"   .
"RP.V"  2004 "Replicel Life Sciences Inc"   .
"Rp.V"  2005 "Replicel Life Sciences Inc"   .
"Rp.V"  2005 "Replicel Life Sciences Inc"   .
"RP.V"  2005 "Replicel Life Sciences Inc"   .
"RP.V"  2006 "Replicel Life Sciences Inc"   .
"Rp.V"  2006 "Replicel Life Sciences Inc"   .
"Rp.V"  2006 "Replicel Life Sciences Inc"   .
"Rp.V"  2007 "Replicel Life Sciences Inc"   .
"Rp.V"  2007 "Replicel Life Sciences Inc"   .
"RP.V"  2007 "Replicel Life Sciences Inc"   .
"Rp.V"  2008 "Replicel Life Sciences Inc"   .
"RP.V"  2008 "Replicel Life Sciences Inc"   .
"Rp.V"  2008 "Replicel Life Sciences Inc"   .
"Rp.V"  2009 "Replicel Life Sciences Inc"   .
"RP.V"  2009 "Replicel Life Sciences Inc"   .
"Rp.V"  2009 "Replicel Life Sciences Inc"   .
"RP.V"  2010 "Replicel Life Sciences Inc"   .
"Rp.V"  2010 "Replicel Life Sciences Inc"   .
"Rp.V"  2010 "Replicel Life Sciences Inc"   .
"RP.V"  2011 "Replicel Life Sciences Inc"   .
"Rp.V"  2011 "Replicel Life Sciences Inc"   .
"Rp.V"  2011 "Replicel Life Sciences Inc"   .
"RP.V"  2012 "Replicel Life Sciences Inc"   .
"Rp.V"  2012 "Replicel Life Sciences Inc"   .
"Rp.V"  2012 "Replicel Life Sciences Inc"   .
"RP.V"  2013 "Replicel Life Sciences Inc"   .
"Rp.V"  2013 "Replicel Life Sciences Inc"   .
"Rp.V"  2013 "Replicel Life Sciences Inc"   .
"Rp.V"  2014 "Replicel Life Sciences Inc"   .
"RP.V"  2014 "Replicel Life Sciences Inc"   .
"Rp.V"  2014 "Replicel Life Sciences Inc"   .
"RP.V"  2015 "Replicel Life Sciences Inc"   .
"Rp.V"  2015 "Replicel Life Sciences Inc"   .
"Rp.V"  2015 "Replicel Life Sciences Inc"   .
"Rp.V"  2016 "Replicel Life Sciences Inc"   .
"Rp.V"  2016 "Replicel Life Sciences Inc"   .
"RP.V"  2016 "Replicel Life Sciences Inc"   .
"Rp.V"  2017 "Replicel Life Sciences Inc"   .
"Rp.V"  2017 "Replicel Life Sciences Inc"   .
"RP.V"  2017 "Replicel Life Sciences Inc"   .
"Rp.V"  2018 "Replicel Life Sciences Inc"   .
"Rp.V"  2018 "Replicel Life Sciences Inc"   .
"RP.V"  2018 "Replicel Life Sciences Inc"   .
"Rp.V"  2019 "Replicel Life Sciences Inc"   .
"RP.V"  2019 "Replicel Life Sciences Inc"   .
"Rp.V"  2019 "Replicel Life Sciences Inc"   .
"Rp.V"  2020 "Replicel Life Sciences Inc"   .
"RP.V"  2020 "Replicel Life Sciences Inc"   .
"Rp.V"  2020 "Replicel Life Sciences Inc"   .
"SAh.V" 1999 "Southern Arc Minerals Inc"    .
"SAH.V" 1999 "Southern Arc Minerals Inc"    .
"SAH.V" 1999 "Southern Arc Minerals Inc"    .
"SAh.V" 1999 "Southern Arc Minerals Inc"    .
"SAh.V" 2000 "Southern Arc Minerals Inc"    .
"SAh.V" 2000 "Southern Arc Minerals Inc"    .
"SAH.V" 2000 "Southern Arc Minerals Inc"    .
"SAH.V" 2000 "Southern Arc Minerals Inc"    .
"SAH.V" 2001 "Southern Arc Minerals Inc"    .
"SAh.V" 2001 "Southern Arc Minerals Inc"    .
"SAh.V" 2001 "Southern Arc Minerals Inc"    .
"SAH.V" 2001 "Southern Arc Minerals Inc"    .
"SAH.V" 2002 "Southern Arc Minerals Inc"    .
"SAh.V" 2002 "Southern Arc Minerals Inc"    .
"SAh.V" 2002 "Southern Arc Minerals Inc"    .
"SAH.V" 2002 "Southern Arc Minerals Inc"    .
"SAh.V" 2003 "Southern Arc Minerals Inc"    .
"SAH.V" 2003 "Southern Arc Minerals Inc"    .
"SAh.V" 2003 "Southern Arc Minerals Inc"    .
"SAH.V" 2003 "Southern Arc Minerals Inc"    .
"SAh.V" 2004 "Southern Arc Minerals Inc"    .
"SAH.V" 2004 "Southern Arc Minerals Inc"    .
"SAh.V" 2004 "Southern Arc Minerals Inc"    .
"SAH.V" 2004 "Southern Arc Minerals Inc"    .
"SAh.V" 2005 "Southern Arc Minerals Inc"    .
"SAH.V" 2005 "Southern Arc Minerals Inc"    .
"SAh.V" 2005 "Southern Arc Minerals Inc"    .
"SAH.V" 2005 "Southern Arc Minerals Inc"    .
"SAh.V" 2006 "Southern Arc Minerals Inc"    .
"SAH.V" 2006 "Southern Arc Minerals Inc"    .
"SAh.V" 2006 "Southern Arc Minerals Inc"    .
"SAH.V" 2006 "Southern Arc Minerals Inc"    .
"SAh.V" 2007 "Southern Arc Minerals Inc"    .
"SAH.V" 2007 "Southern Arc Minerals Inc"    .
"SAh.V" 2007 "Southern Arc Minerals Inc"    .
"SAH.V" 2007 "Southern Arc Minerals Inc"    .
"SAh.V" 2008 "Southern Arc Minerals Inc"    .
"SAH.V" 2008 "Southern Arc Minerals Inc"    .
"SAH.V" 2008 "Southern Arc Minerals Inc"    .
"SAh.V" 2008 "Southern Arc Minerals Inc"    .
"SAH.V" 2009 "Southern Arc Minerals Inc"    .
"SAH.V" 2009 "Southern Arc Minerals Inc"    .
"SAh.V" 2009 "Southern Arc Minerals Inc"    .
"SAh.V" 2009 "Southern Arc Minerals Inc"    .
"SAh.V" 2010 "Southern Arc Minerals Inc"    .
"SAH.V" 2010 "Southern Arc Minerals Inc"    .
"SAH.V" 2010 "Southern Arc Minerals Inc"    .
"SAh.V" 2010 "Southern Arc Minerals Inc"    .
"SAh.V" 2011 "Southern Arc Minerals Inc"    .
"SAH.V" 2011 "Southern Arc Minerals Inc"    .
"SAH.V" 2011 "Southern Arc Minerals Inc"    .
"SAh.V" 2011 "Southern Arc Minerals Inc"    .
"SAH.V" 2012 "Southern Arc Minerals Inc"    .
"SAh.V" 2012 "Southern Arc Minerals Inc"    .
"SAH.V" 2012 "Southern Arc Minerals Inc"    .
"SAh.V" 2012 "Southern Arc Minerals Inc"    .
"SAH.V" 2013 "Southern Arc Minerals Inc"    .
"SAh.V" 2013 "Southern Arc Minerals Inc"    .
"SAh.V" 2013 "Southern Arc Minerals Inc"    .
"SAH.V" 2013 "Southern Arc Minerals Inc"    .
"SAh.V" 2014 "Southern Arc Minerals Inc"    .
"SAH.V" 2014 "Southern Arc Minerals Inc"    .
"SAH.V" 2014 "Southern Arc Minerals Inc"    .
"SAh.V" 2014 "Southern Arc Minerals Inc"    .
"SAh.V" 2015 "Southern Arc Minerals Inc"    .
"SAh.V" 2015 "Southern Arc Minerals Inc"    .
"SAH.V" 2015 "Southern Arc Minerals Inc"    .
"SAH.V" 2015 "Southern Arc Minerals Inc"    .
"SAh.V" 2016 "Southern Arc Minerals Inc"    .
"SAh.V" 2016 "Southern Arc Minerals Inc"    .
"SAH.V" 2016 "Southern Arc Minerals Inc"    .
"SAH.V" 2016 "Southern Arc Minerals Inc"    .
"SAH.V" 2017 "Southern Arc Minerals Inc"    .
"SAh.V" 2017 "Southern Arc Minerals Inc"    .
"SAh.V" 2017 "Southern Arc Minerals Inc"    .
"SAH.V" 2017 "Southern Arc Minerals Inc"    .
"SAh.V" 2018 "Southern Arc Minerals Inc"    .
"SAh.V" 2018 "Southern Arc Minerals Inc"    .
"SAH.V" 2018 "Southern Arc Minerals Inc"    .
"SAH.V" 2018 "Southern Arc Minerals Inc"    .
"SAh.V" 2019 "Southern Arc Minerals Inc"    .
"SAH.V" 2019 "Southern Arc Minerals Inc"    .
"SAH.V" 2019 "Southern Arc Minerals Inc"    .
"SAh.V" 2019 "Southern Arc Minerals Inc"    .
"SAh.V" 2020 "Southern Arc Minerals Inc"    .
"SAH.V" 2020 "Southern Arc Minerals Inc"    .
"SAh.V" 2020 "Southern Arc Minerals Inc"    .
"SAH.V" 2020 "Southern Arc Minerals Inc"    .
end

*note that both ric and companyname are identifiers


* I would like set the panel and I tried 
encode companyname, gen (id)
encode ric, gen (id2)

xtset id year 
repeated time values within panel
r(451);

xtset id2 year 
repeated time values within panel
r(451);

*Removing duplicates
duplicates report id year 
/*
-------------------------------------
   Copies | Observations       Surplus
----------+---------------------------
        2 |           88            44
        3 |           66            44
        4 |           88            66
*/
sort id year
quietly by id year: gen dup = cond(_N==1,0,_n)
drop if dup>1
*(154 observations deleted)
xtset id year 
/*
xtset id year 

Panel variable: id (strongly balanced)
 Time variable: year, 1999 to 2020
         Delta: 1 unit
*/


xtset id2 year 
/*
 xtset id2 year 

Panel variable: id2 (unbalanced)
 Time variable: year, 1999 to 2020, but with gaps
         Delta: 1 unit

. 
*/
Why this difference? When I tried using user written command -distinct- (ssc install distinct), I got the following output
distinct id id2 
/*

       |        Observations
       |      total   distinct
-------+----------------------
    id |         88          4
   id2 |         88          6
*/
*Though both id and id2 are unique identifiers for each unit(companyname) why is id2 (ric)> id (companyname)