Dear all,

I have a 4-wave panel data and I want to identify individuals who ever work, i.e. someone may work in 2007 but then quit his/her job in 2009 or the other way around, an individual may not work in 2007 but start working in 2009. Any help is appreciated.

Code:
clear
input int id float(year work)
  5 2007 1
  5 2009 0
  5 2011 0
  5 2013 0
  9 2009 1
  9 2011 0
  9 2013 0
 18 2009 1
 18 2011 0
 18 2013 1
 21 2009 0
 21 2011 0
 21 2013 0
 26 2009 0
 26 2011 1
 29 2009 0
 29 2011 0
 30 2009 0
 30 2011 0
 30 2013 1
 31 2009 0
 31 2011 0
 31 2013 0
 38 2009 1
 38 2011 0
 38 2013 0
 39 2009 0
 39 2011 0
 43 2007 1
 43 2009 0
 43 2011 0
 43 2013 1
 45 2007 0
 45 2009 1
 45 2011 1
 45 2013 0
 49 2009 0
 49 2011 0
 49 2013 1
 53 2009 0
 53 2011 0
 53 2013 0
 54 2009 1
 54 2011 0
 54 2013 0
 56 2009 0
 56 2011 0
 56 2013 1
 60 2007 0
 60 2009 0
 60 2011 1
 60 2013 0
 61 2009 0
 61 2011 0
 61 2013 0
 66 2009 0
 66 2011 0
 67 2009 0
 67 2011 0
 67 2013 0
 70 2009 0
 70 2011 0
 70 2013 0
 71 2007 0
 71 2009 0
 71 2011 0
 71 2013 0
 76 2009 0
 76 2011 0
 76 2013 0
 84 2009 0
 84 2011 0
 84 2013 0
 87 2009 0
 87 2011 0
 90 2009 0
 90 2011 0
 90 2013 0
 92 2009 0
 92 2011 0
 92 2013 0
 94 2009 0
 94 2011 0
 94 2013 0
 95 2009 0
 95 2011 0
 95 2013 0
 98 2009 0
 98 2011 0
 98 2013 0
101 2009 0
101 2011 0
101 2013 0
102 2009 0
102 2011 0
102 2013 0
111 2007 0
111 2009 0
111 2011 0
112 2007 0
end