For an over-time analysis of 2000-2015 ACS data I would like to know why the number (and share) of married couples (both different-sex and same-sex) with at least one member having a flag on marital status (QMARST=4) increased so much in 2015. It increased from about 0.3% in 2013/2014 to 8.0% in 2015 and from 3.0% to 13.8% for different-sex and same-sex couples, respectively.
Do you know why this is the case? Was there a change in the data collection or editing procedure in 2015? What would you recommend to obtain the most reliable sample of same-sex couples?