public function getCurrencyCovIndex()
    {
        if ($this->_dConvIndex === null) {
            // currency conversion index value
            $oCur = \OxidEsales\Eshop\Core\Registry::getConfig()->getActShopCurrencyObject();
            $this->_dConvIndex = 1 / $oCur->rate;
        }

        return $this->_dConvIndex;
    }