employer variable:group
list, sepby(employer) noobs
list year employer length longspell, sepby(employer) noobs
generate byte beginspell = employer != employer[_n-1]
generate byte beginunemp = missing(employer) & ((employer != employer[_n-1]) | (_n == 1))
by spellnr: gen length = _N if !missing(employer)
@freq 4, 5, 1, 2, 3 @values "A", "B", "C", "D", "E" @type str1 @label @class category @N_unique 5 @N 15