Distribution of metal-enriched white dwarfs in wide binaries from Table A.1 as a function of projected separation. The top panel shows the estimated initial projected separation been when both stars in the binary were on the main sequence, whereas the bottom panel shows the observed projected separation. The vertical line corresponds to a separation of 1000 au, which Zuckerman (2014) identified as a thresh-old below which the frequency of metal-enrichment decreases.