def overlap(self):
        """
        Read/write int value in range -100..100 specifying a percentage of
        the bar width by which to overlap adjacent bars in a multi-series bar
        chart. Default is 0. A setting of -100 creates a gap of a full bar
        width and a setting of 100 causes all the bars in a category to be
        superimposed. A stacked bar plot has overlap of 100 by default.
        """
        overlap = self._element.overlap
        if overlap is None:
            return 0
        return overlap.val