Yu states that a supply chain consists of at least three players, namely the supplier, the
manufacturer, and the customer. It is more complicated when the supply chain is extended in the
real world. There will be wholesalers, traders, distributors, and even service providers involved in
the chain. So the longan supply chain, from upstream to downstream, will include many players,
from Thai growers to Chinese importers. This means that even a small change could affect all the
players in the supply chain. It thus becomes much more interesting to understand the economic
impact of barriers to international trade on those players, especially among countries where tariffs
are almost equal to zero.