// E.g., 9s (45%) 🠆 10s (50%)
  function diffText(from, to) {
    return percentText(from) + " 🠆 " + percentText(to);
  }

  // percentText returns text that displays v in appropriate units alongside its
  // percentange.
  function percentText(v) {
    function percent(v, total) {
      return Number(((100.0 * v) / total).toFixed(1)) + '%';
    }
    return unitText(v) + " (" + percent(v, stacks.Total) + ")";
  }