, i) {
        // sort all the areas relative to the current item
        venn.sortAreas(div, d);

        // Display a tooltip with the current size
        tooltip.transition().duration(400).style("opacity", .9);
        tooltip.text(d.size + " users");

        // highlight the current path
        var selection = d3.select(this).transition("tooltip").duration(400);
        selection.select("path")
            .style("fill-opacity", d.sets.length == 1 ? .4 : .1)
            .style("stroke-opacity", 1);
 