protected function getDivisor($row)
    {
        if (!is_null($this->totalValueUsedAsDivisor)) {
            return $this->totalValueUsedAsDivisor;
        } elseif ($this->getDivisorFromSummaryRow) {
            $summaryRow = $this->table->getRowFromId(DataTable::ID_SUMMARY_ROW);
            return $summaryRow->getColumn($this->columnNameUsedAsDivisor);
        } else {
            return $row->getColumn($this->columnNameUsedAsDivisor);
        }
    }