Excerpted from the Wikipedia article entitled “Balance of trade”:
Trade Balances' effects upon their nation’s GDP.
Annual trade surpluses are immediate and direct additions to their nations’ GDPs. To some extent exports induce additional increases to GDP that are not reflected within the export products’ prices; thus contributions to GDP from trade surpluses are generally understated.
Products’ prices generally reflect their producers’ production supporting expenditures. Producers often benefit from some production supporting goods and services at lesser or no cost to the producers.
For example, governments may deliberately locate or increase the capacity of their infrastructure, or provide other additional considerations to retain or attract producers within their own jurisdictions. The curriculum of a nation's schools and colleges may provide job applicants specifically suited to the producer’s needs, or provide specialized research and development. All national
factors of production, including education, contribute to GDP, and unless globally traded products fully reflect those goods and services, these other export supporting contributions are not entirely identified and attributed to their nations’ global trade.
Annual trade deficits are immediate and indirect reducers of their nations’ GDPs.
Trade deficits make no net contribution to their nations’ GDPs but the importing nations indirectly deny themselves of the benefits earned by producing nations; (refer to “Annual trade surpluses are immediate and direct additions to their nations’ GDPs”). Among what’s being denied is familiarity with methods, practices, the manipulation of tools, materials and fabrication processes.
The economic differences between domestic and imported goods occur prior to the goods entry within the final purchasers' nations. After domestic goods have reached their producers shipping dock or imported goods have been unloaded on to the importing nation’s cargo vessel or entry port’s dock, similar goods have similar economic attributes.
Although supporting products not reflected within the prices of specific items are all captured within the producing nation’s GDP, those supporting but not reflected within prices of globally traded goods are not attributed to nations' global trade. Trade surpluses' contributions and trade deficits' detriments to their nation's GDPs are understated. The entire benefits of production are earned by the exporting nations and denied to the importing nation.