China would lose 2.2 percent of its gross domestic product if 15 other countries joined the Trans-Pacific Partnership without China, according to the central bank's chief economist.

That view is part of an academic paper published by the Shanghai Securities Journal on Friday, a few days after 12 Pacific Rim countries wrapped up negotiations over their trade agreement on Monday. China is not among the 12 nations.

The figure of 2.2 percent of GDP was arrived at based on the gap between the net effects of two different scenarios: one that assumes 16 nations, including China, joined the partnership, the other that assumes 15 nations, including the current 12 nations plus South Korea, Indonesia and Thailand, joined the group.