This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.
Q: Passage: After their ouster from the coastal ports of China, Japanese and Portuguese traders collaborated with illegal smugglers on island ports along the Zhejiang and Fujian coast. Among these ports, Shuangyu on Liuheng Island off the coast of Ningbo emerged as the primary emporium of clandestine trade. At first, Shuangyu only had temporary mat-sheds for the smugglers to house themselves and their goods during the trading season. In 1539, Fujianese traders started to guide foreign traders from Patani and Malacca to barter in Shuangyu and started to occupy the island. They were soon joined by the Fujianese merchants Jinzi Lao and Li Guangtou , who led the Portuguese and assorted adventurers to Shuangyu. Attracted by the growing trade on the Zhejiang coast, the Xu brothers' syndicate moved their base of operations from the Malay Peninsula to Shuangyu. The existing clout of the Xu syndicate and its close partnership with the Portuguese made it the foremost smuggling bloc by 1542 after a series of mergers among the merchant-pirates in Shuangyu. The Ming navy began to clamp down on smuggling activities in 1543, but the Xu syndicate was able to repulse the Ming attacks in Shuangyu with the aid of Portuguese firepower. Hardened by their victories against the Ming navy, the smugglers expanded their network of activities down the coast of China all the way to Guangdong and inland to the metropolis of Nanjing, with Shuangyu being their hub. In 1544, this network was further expanded when Wang Zhi joined the Xu syndicate, bringing along his Japanese connections to Shuangyu. Thus Shuangyu reached its zenith as the biggest entrepot in maritime East Asia trading goods from Europe and Asia until its downfall in 1548.
Question: How many years did Shangyu last as the biggest entrepot?
Answer type: Number
A:
4.