protected function getDividend($row)
    {
        $currentValue = $row->getColumn($this->columnValueToRead);

        // if the site this is for doesn't support ecommerce & this is for the revenue_evolution column,
        // we don't add the new column
        if ($currentValue === false
            && $this->isRevenueEvolution
            && !Site::isEcommerceEnabledFor($row->getColumn('label'))
        ) {
            return false;
        }

        $pastRow = $this->getPastRowFromCurrent($row);
        if ($pastRow) {
            $pastValue = $pastRow->getColumn($this->columnValueToRead);
        } else {
            $pastValue = 0;
        }

        return $currentValue - $pastValue;
    }