Hi, I have an indicator variable EventIndicator, which takes the value 1 if a firm is headquartered in a state adopts certain regulations in that year and takes the value 0 otherwise.

gen EventIndicator=state=="AZ" & fyear>2005|state=="AR" & fyear>2004|state=="CA" & fyear>1991|state=="CT" & fyear>2016|state=="DE" & fyear>1991|state=="FL" & fyear>1999|state=="GA" & fyear>1995|state=="HI" & fyear>2001|state=="IL" & fyear>2006|state=="IN" & fyear>1997|state=="KS" & fyear>2015|state=="LA" & fyear>1998|state=="ME" & fyear>1994|state=="MD" & fyear>2003|state=="MA" & fyear>1993|state=="MO" & fyear>2003|state=="NE" & fyear>1993|state=="NV" & fyear>1992|state=="NM" & fyear>2000|state=="NY" & fyear>1991|state=="OK" & fyear>2013|state=="OR" & fyear>2000|state=="PA" & fyear>1999|state=="RI" & fyear>1994|state=="TX" & fyear>2010|state=="TN" & fyear>1996|state=="UT" & fyear>2000|state=="VT" & fyear>2004|state=="WA" & fyear>2009 & fyear<2016|state=="MN" & fyear>1993 & fyear<2018


I want to include EventIndicator t, EventIndicator t+1, and EventIndicator t+2 all in the same regression. However, I was wondering why the number of observations of EventIndicator at year t, EventIndicator t+1, and EventIndicator t+2 are different. Please see below for the data sample.

Thank you!



Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long(gvkey datadate) double fyear str8 state long n_state float EventIndicator
1004 15126 2000 "IL" 17 0
1004 15491 2001 "IL" 17 0
1004 15856 2002 "IL" 17 0
1004 16222 2003 "IL" 17 0
1004 16587 2004 "IL" 17 0
1004 16952 2005 "IL" 17 0
1004 17317 2006 "IL" 17 0
1004 17683 2007 "IL" 17 1
1004 18048 2008 "IL" 17 1
1004 18413 2009 "IL" 17 1
1004 18778 2010 "IL" 17 1
1004 19144 2011 "IL" 17 1
1004 19509 2012 "IL" 17 1
1004 19874 2013 "IL" 17 1
1004 20239 2014 "IL" 17 1
1004 20605 2015 "IL" 17 1
1004 20970 2016 "IL" 17 1
1004 21335 2017 "IL" 17 1
1004 21700 2018 "IL" 17 1
1004 22066 2019 "IL" 17 1
1010 14975 2000 "MO" 28 0
1010 15340 2001 "MO" 28 0
1010 15705 2002 "MO" 28 0
1010 16070 2003 "MO" 28 0
1013 14914 2000 "MN" 27 1
1013 15279 2001 "MN" 27 1
1013 15644 2002 "MN" 27 1
1013 16009 2003 "MN" 27 1
1013 16375 2004 "MN" 27 1
1013 16740 2005 "MN" 27 1
1013 17105 2006 "MN" 27 1
1013 17470 2007 "MN" 27 1
1013 17836 2008 "MN" 27 1
1013 18170 2009 "MN" 27 1
1013 18535 2010 "MN" 27 1
1019 14975 2000 "NY" 41 1
1019 15340 2001 "NY" 41 1
1021 14791 2000 "NY" 41 1
1021 15156 2001 "NY" 41 1
1021 15521 2002 "NY" 41 1
1021 15886 2003 "NY" 41 1
1021 16252 2004 "NY" 41 1
1021 16617 2005 "NY" 41 1
1021 16982 2006 "NY" 41 1
1021 17347 2007 "NY" 41 1
1021 17713 2008 "NY" 41 1
1034 14975 2000 "NJ" 37 0
1034 15340 2001 "NJ" 37 0
1034 15705 2002 "NJ" 37 0
1034 16070 2003 "NJ" 37 0
1034 16436 2004 "NJ" 37 0
1034 16801 2005 "NJ" 37 0
1034 17166 2006 "NJ" 37 0
1034 17531 2007 "NJ" 37 0
1036 14975 2000 "NC" 32 0
1037 15065 2000 "PA" 46 1
1037 15430 2001 "PA" 46 1
1038 15065 2000 "MO" 28 0
1038 15430 2001 "MO" 28 0
1038 15795 2002 "MO" 28 0
1038 16161 2003 "MO" 28 0
1045 14975 2000 "TX" 54 0
1045 15340 2001 "TX" 54 0
1045 15705 2002 "TX" 54 0
1045 16070 2003 "TX" 54 0
1045 16436 2004 "TX" 54 0
1045 16801 2005 "TX" 54 0
1045 17166 2006 "TX" 54 0
1045 17531 2007 "TX" 54 0
1045 17897 2008 "TX" 54 0
1045 18262 2009 "TX" 54 0
1045 18627 2010 "TX" 54 0
1045 18992 2011 "TX" 54 1
1045 19358 2012 "TX" 54 1
1045 19723 2013 "TX" 54 1
1045 20088 2014 "TX" 54 1
1045 20453 2015 "TX" 54 1
1045 20819 2016 "TX" 54 1
1045 21184 2017 "TX" 54 1
1045 21549 2018 "TX" 54 1
1045 21914 2019 "TX" 54 1
1050 14975 2000 "TX" 54 0
1050 15340 2001 "TX" 54 0
1050 15705 2002 "TX" 54 0
1050 16070 2003 "TX" 54 0
1050 16436 2004 "TX" 54 0
1050 16801 2005 "TX" 54 0
1050 17166 2006 "TX" 54 0
1050 17531 2007 "TX" 54 0
1050 17897 2008 "TX" 54 0
1050 18262 2009 "TX" 54 0
1050 18627 2010 "TX" 54 0
1050 18992 2011 "TX" 54 1
1050 19358 2012 "TX" 54 1
1050 19723 2013 "TX" 54 1
1050 20088 2014 "TX" 54 1
1050 20453 2015 "TX" 54 1
1050 20819 2016 "TX" 54 1
1050 21184 2017 "TX" 54 1
1050 21549 2018 "TX" 54 1
end
format %td datadate
label values n_state n_state
label def n_state 17 "IL", modify
label def n_state 27 "MN", modify
label def n_state 28 "MO", modify
label def n_state 32 "NC", modify
label def n_state 37 "NJ", modify
label def n_state 41 "NY", modify
label def n_state 46 "PA", modify
label def n_state 54 "TX", modify