I ran the following equations via fixed effects (one with a lead for union status, and one without a lead for union status)
xtreg lwage educ black Hispanic experience married union, fe
xtreg lwage educ black Hispanic experience married unionlead, fe

for the equation without the lead, union status was significant at every level, however, when a lead was used, it was not significant at .01 (significant at .05) Does this mean union status is not strictly exogenous?

Thank you.