private function getBirthChartData(): array
    {
        // Count how many people were born in each country
        $surn_countries = [];
        $b_countries    = $this->placeRepository->statsPlaces('INDI', 'BIRT', 0, true);

        foreach ($b_countries as $country => $count) {
            // Consolidate places (Germany, DEU => DE)
            if (array_key_exists($country, $this->country_to_iso3166)) {
                $country_code = $this->country_to_iso3166[$country];

                if (array_key_exists($country_code, $surn_countries)) {
                    $surn_countries[$country_code] += $count;
                } else {
                    $surn_countries[$country_code] = $count;
                }
            }
        }

        return $this->createChartData($surn_countries);
    }