public String getTooltipExtraText(final Province current) {
        final int id = current.getId();
        if (!editor.Main.map.isLand(id))
            return "";
        
        String value = mapPanel.getModel().getHistString(id, prop);
        if (value == null || value.length() == 0)
            value = "0";
        return prop + ": " + value;
    }