Hey guys,

I'm trying to put together a diff-in-diff panel where the treatment is a labour market program beginning in 2015. I've reduced the panel so that it only includes those over the period 2011-2018, unemployed between 2011-2014 as baseline and only engaging in labour market program after 2015 for the treated. The problem is I have some individuals who have only recorded observations past 2015. I'm not too concerned about the length or balance of years, but I just want to ensure that for both treatment and control, there is at least an entry for 2014 and 2015. My code/data so far looks like this:

Code:
egen id = group(xwaveid), label

**refine years observed
gen year = 0
replace year = 2011 if wave==11
replace year = 2012 if wave==12
replace year = 2013 if wave==13
replace year = 2014 if wave==14
replace year = 2015 if wave==15
replace year = 2016 if wave==16
replace year = 2017 if wave==17
replace year = 2018 if wave==18
drop if year==0

**Refine to only those not engaging with LMP prior to 2015
bysort id (jsactrc) : drop if jsactrc==1 & year>=2011&year<=2014

**Refine by only those unemployed prior to 2015
bysort id (esbrd) : drop if esbrd!=2 & year>=2011&year<=2014

sort id year
**Treatment
gen treat_ja = 0
replace treat_ja = 1 if jsactrc==1 & year>=2015&year<=2018
egen T_ja = max(treat_ja), by (id)

**Drop later observations
bysort id (year): drop if missing(year==2014 & year==2015)

Code:
input byte hgsex int hgage byte(esbrd esdtl jsactrc ehtujyr es esempdt) float(id year treat_ja T_ja)
1 28 1 1 -1 -1  1  1 1 2014 0 0
1 29 1 1 -1 -1  1  1 1 2015 0 0
1 30 1 1 -1 -1  1  1 1 2016 0 0
1 31 2 3  0 -1 -1 -1 1 2017 0 0
1 32 1 1 -1 -1  1  1 2 2018 0 0
1 27 1 1 -1 -1  1  1 2 2011 0 0
1 28 1 1 -1 -1  1  1 2 2012 0 0
1 29 1 1 -1 -1  1  1 2 2013 0 0
1 30 1 1 -1 -1  1  1 3 2014 0 0
1 31 1 1 -1 -1  1  1 3 2015 0 0
1 32 1 1 -1 -1  1  1 3 2016 0 0
1 33 1 1 -1 -1  1  1 3 2017 0 0
2 34 1 2 -1 -1  1  1 4 2018 0 0
2 22 1 1 -1 -1  1  1 4 2016 0 0
2 23 1 1 -1 -1  1  1 4 2017 0 0
2 24 1 1 -1 -1  1  1 4 2018 0 0
2 57 1 1 -1 -1  1  1 7 2015 0 0
2 58 1 1 -1 -1  1  1 7 2016 0 0
2 59 1 1 -1 -1  1  1 7 2017 0 0
2 60 3 6 -1 -1 -1 -1 7 2018 0 0
When I try to drop conditional on missing year 2014 and 2015 it drops 0 observations. I'm assuming this is because the year entry is missing entirely? Other than that I'm out of ideas. Any help with this would be really appreciated!

Cheers,
Toby