public function getGeometricMean($Serie)
    {
        if (isset($this->Data["Series"][$Serie])) {
            $SerieData = $this->stripVOID($this->Data["Series"][$Serie]["Data"]);
            $Seriesum = 1;
            foreach ($SerieData as $Value) {
                $Seriesum = $Seriesum * $Value;
            }
            return pow($Seriesum, 1 / sizeof($SerieData));
        }

        return null;
    }