I believe the answer is: Producers reduce their costs.
Specialization refers to the process of focusing all of our current resource in producing a specific type of goods while reducing the production for others, which would make the cost to produce the specialized product become lower in the long run.
Specialization tend to be done if a country had a competitive advantage to produce a certain type of products compared to other country.For example, Malaysia is known for doing a specialization in latex-related product because they have better natural environments for latex trees to grow,.