The accolade "world's busiest cargo harbor" is hotly disputed. Leading ports like Rotterdam and Singapore are eager to claim the title. Both promote themselves as transshipment centers, and stress the convenience of transportation to nearby places which lack ocean access or the special facilities needed to handle the biggest freight vessels (in the case of Rotterdam, road and rail links to Germany's Ruhr region). 

The rise and decline of particular ports tracks general economic trends. Rotterdam was the world's busiest shipping center by total cargo tonnage between 1962 - when Germany's postwar recovery was going full steam - and 2002, by which time Asia was no only more important in manufacturing goods but also a bigger market for consuming them. In terms of containers shifted, Kobe in Japan held the no. 1 spot between 1973 and 1978. As "Made in Taiwan" has given way to "Made in China," so Kaohsiung - Taiwan's leading harbor ever since it was opened to foreign trade in the 19th century - has slipped from being the world's third-busiest container port in the 1980s (behind Hong Kong and Singapore) to 22nd in 2008.

hanjinsfCredit: John MorganAccording to the World Shipping Council, which brings together 29 of the world's most important cargo-shipping companies, the busiest container-handling port in 2012 was Shanghai. That year it dealt with 32.53 million TEUs; TEU stands for twenty-foot equivalent unit, the amount of cargo that can be put inside a standard 20-foot-long (6.1m) freight container. In 2011 and 2012, Shanghai was slightly ahead of Singapore. In both years, Hong Kong held the no. 3 position, while Shenzhen (the PRC port closest to Hong Kong) was no. 4. Of harbors ranked fifth to tenth, four are in China; the others are Busan in South Korea at no. 5 and Jebel Ali, Dubai, United Arab Emirates (no. 9).

In terms of container traffic, Rotterdam at no. 11 is the busiest anywhere in Europe, although Hamburg and Antwerp aren't far behind. North America's leading container port is Los Angeles (no. 16, handling just a quarter as many TEUs as Shanghai). India is often spoken of as a future economic superpower, but it's top harbor, Jawaharlal Nehru (named for the country's first prime minister and located in Mumbai), ranks way down at no. 33, with just 4.26 million TEUs in 2012.

Australia's main container facility at Melbourne ranks just ahead of Durban (no. 50 and the only African port on the list; 2.59 million TEUs). Many of Australia's exports take the form of bulk commodities such as coal which don't travel in containers. For this reason, Port Hedland in Western Australia is considered one of the Top 10 harbors on Earth. In 2011, the harbor  handled over 199 million tons of cargo, much of it iron ore. The Port of South Louisiana is also far more important than its modest container-handling tally suggests; it ships more than half of the USA's exports of grain, wheat, soy and corn.

Overall, Shanghai is the world's busiest cargo harbor. In 2012, it handled at least 736 million tons of manufactured goods, bulk commodities and containers.