利用中日史料中留存的相关数据，将 1700 年夏清内务府商人张鼎臣兄弟名下船只的赴日铜贸
易活动作模拟还原后可知，当时商人们将以生丝和白砂糖这两个主要出口货物换回的日本铜按照国内税关
的收购价售出，这个过程获得的利润要比张氏兄弟在奏折中向康熙帝宣称的 30% 要高得多，亦并非真如其
所言，办铜一项上所获利润在支出 “节省银”、高利贷利息等费用后，竟变得无利可图，而是在购铜成本，
即早在大宗收购生丝等赴日贸易品花费上就已隐瞒了相当的利润。可以说，在1700 年至1715 年内务府商人
承包办铜的十余年间，只要日本方面铜的供给量不发生大的下滑，那么铜这一商品将给这些 “皇商”们带
来长期稳定的高利润回报。但日本铜供给量不断下滑的事实，导致内务府商人在办铜后期积欠了大量的铜
额。在此情况下，即便铜贸易本身仍有利可图，但作为清廷而言已必须要重新考虑变换办铜体制了。

Using data Japanese and Chinese historical documents，we can reconstruct the trading activities of
Imperial Household Department merchant，Zhang Dingchen with Japan during the summer of 1700． This
date reveals that the profit from the trade，which exchanged raw silk and white sugar for Japanese copper，
were much more than 30% reported to the Emperor Kangxi． Actually，the large profit was hidden． In
fact，the copper would bring higher return，which was stable and long-term，to the “Imperial Merchant”
from 1700-1715，as long as the supply of the copper in Japan did not decline sharply．