No it is not just about sales... well, not completely.
OICA (Organisation Internationale des Constructeurs d’Automobiles or International Organization of Motor Vehicle Manufacturers) is the organization responsible for ranking global automakers annually based on the number of vehicles produced rather than the units delivered or sold to dealers and/or customers.
The reason 'deliveries' and 'sales' data isn't reliable is because vehicles manufactured in 2015 for example, may just have been delivered and/or sold in 2016, which makes it a statistic for 2015 and not 2016 as far as OICA and this list is concerned.
Various automakers differ in the data they provide OICA, as some rely on sales information while others submit manufacturing numbers.
As per the rankings of OICA released early this year, Volkswagen Group unseats Toyota after four consecutive years of holding the title as the 'world's largest automaker.' Here are the top three:
January to December 2016
10,312,400 units - Volkswagen Group
10,213,486 units - Toyota:
9,574,771 units - General Motors
Volkswagen Group reported a record 10.31 million units in sales last year, up 3.8-percent from 2015. Sales rose by 4-percent in Europe, 0.8-percent in North America, 5-percent in South America, 9.7-percent in the Asia-Pacific, which includes a whooping 12.2-percent increase in the Chinese market. VW has managed to take advantage of a tax cut implemented in late 2015 until end of 2016 where sales taxes were halved for small cars.
In the Philippines, Volkswagen broke through the 1,000 unit sales mark in 2016 as continued expansion of its dealer network and aggressive sales promotions boosted sales to a total of 1,060 units.
Brands under the Volkswagen Group are: Audi, Bentley, Bugatti, Ducati, Lamborghini, MAN, Porsche, Scania, Skoda, Seat, Volkswagen Commercial and Volkswagen.
Despite getting overall annual record-high manufacturing numbers outside Japan from Toyota, Daihatsu and Hino, the 3% decrease in worldwide production from Toyota in the month of December hurt their numbers and 0.7% reduction in Toyota manufacturing in Japan also negatively affected their yearly results.
Brands under Toyota: Daihatsu, Hino, Lexus, Scion (until October 2016) and Toyota.
General Motors is riding high on the wave of a US automotive sales boom in 2016, recording a 10% year-on-year increase led by the strong sales of Chevrolet (Colorado - 20%, Trax - 43%, Equinox - 38%, Traverse - 22%), which picked up an brand-best 8% increase in sales just in December 2016 alone.
Brands under the GM umbrella are: Chevrolet, Buick, GMC, Cadillac, Holden, HSV,Opel, Vauxhall, Wuling, Baojun, Jie Fang and Ravon.