Container traffic through a port is often tracked in terms of twenty foot equivalent units or TEU of throughput.[90] As of 2009[update], the Port of Singapore was the world's busiest container port, with 25,866,000 TEU handled.[90] That year, six of the busiest ten container ports were in the People's Republic of China, with Shanghai in 2nd place, Port of Hong Kong in 3rd, Shenzhen 4th, Guangzhou 6th, Ningbo 8th, and Qingdao 9th.[90] Rounding out the top ten ports were Busan in South Korea at number 5, Dubai in the United Arab Emirates at number 7, and Rotterdam in the Netherlands in the 10th position with 9,743,290 TEU served.[90] In total, the busiest twenty container ports handled 220,905,805 TEU in 2009, almost half of the world's total estimated container traffic that year of 465,597,537 TEU.[90]