日本商館利潤是十七世紀荷蘭東印度公司融通亞洲貿易最重要的 資金來源, 利用荷蘭檔案館之原始資料, 我們整理出荷蘭東印度公 司在日本商館的商品利潤。生絲是當時最重要的商品, 在1641年 之前, 荷蘭人販售的生絲主要是在台灣買到的中國絲, 這說明了早 期台灣做為轉口港之重要性。除了轉口貿易之外, 台灣本身亦出口 鹿皮、糖等商品; 不過重要性遠不及早期的絲。荷蘭人與鄭芝龍交 惡後失去了中國絲的貨源, 台灣的商業地位因此不免大減。這部分 說明了何以在投降鄭氏家族之後,荷蘭人未積極地策劃重占台灣。

The Dutch East India Company relied heavily on the profits at her Japan Factory to finance her intra-Asia trade in the seventeenth century. We use the primary sources to compile profits of various commodities sold in Japan, and identify raw silk as the most profitable. Since before 1641, the Company obtained Chinese silk from Taiwan, Taiwan's importance as an entrepot cannot be over-emphasized. Taiwan also provided local products like deerskins and sugar to Japan's market, but their importance cannot be compared with that of raw silk. After breaking off with Iquan, the Dutch lost their sources of Chinese silk, and this diminished Taiwan’s once important role as an entrepot. This partially explains why the Dutch never seriously planned to return to Taiwan after the surrender to the Koxinga’s family.