Derivation
variable: joinest [decade estimate of joining household] (table[s]: tb_tbx, tb_tbxto2007, tbold_part1/2, tb_tbo, tb_tboto2007, tbold_control)
variable: joinmm [month of joining household] (table[s]: tb_tbx, tb_tbxto2007, tbold_part1/2, tb_tbo, tb_tboto2007, tbold_control)
variable: joinyear [year of joining household] (table[s]: tb_tbx, tb_tbxto2007, tbold_part1/2, tb_tbo, tb_tboto2007, tbold_control)