Distribution of matching groups as a function of group richness in Tully (2015b) and in our FoF catalogue. In the left panel, counterparts for each Tully group are sought from the FoF catalogue, in the right panel vice versa. Different lines correspond to groups with zero, one, two, or more matches in the comparison catalogue (see text for more details). Groups with more matches are generally richer, groups with zero matches poorer systems. The inset pie diagrams show the fractions of groups with a given amount of counterparts. Table 1 shows the numbers and fractions of groups contained in each sector.