Is there any confirmed saying on this problem?
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1$\begingroup$ en.wikipedia.org/wiki/International_trade#Ricardian_model $\endgroup$ – Jamzy Oct 12 '15 at 4:04
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In short: Yes and due to comparative advantage.
The level of GDP growth gained with opening trade does vary by country and time. I'd suggest Wacziarg & Welch (2008). Trade Liberalization and Growth: New Evidence, World Bank Economic Review, vol. 22(2) for a relatively new study on the subject.
