by 2025, TPP would raise U.S. incomes by 0.4 percent per year

See TPP is a trade agreement by Greg Mankiw.

"Oddly, Paul Krugman thinks that TPP is not really about trade. CEA Chair Jason Furman, however, writes the following:

The starting point of TPP is the contrast between U.S. tariffs and those of our partner countries. Our trade-weighted average applied tariff rate is 1.4 percent and 70 percent of imports already enter our economy duty free. In contrast, on average, our TPP partners report simple average applied tariffs 1.5 percentage points higher than our equivalent rate. In some TPP countries, average tariffs are up to 4 percentage points higher, though this difference masks considerable industry-specific variation; the United States faces tariffs of up to 30 percent on auto exports to Malaysia and 40 percent on agricultural goods to Vietnam. Many TPP countries also have substantially higher non-tariff barriers, particularly in the area of services trade, where the United States maintains a strong comparative advantage. As a result, TPP will disproportionately decrease foreign barriers to U.S. exports....  

The most comprehensive estimates of the benefits of TPP are those of Peter Petri, Michael Plummer, and Fan Zhai, who employ an 18-sector, 24-region computable general equilibrium model to simulate policy changes in more than twenty different areas including tariffs, non-tariff barriers, and rules governing foreign direct investment. They find that by 2025, TPP would raise U.S. incomes by 0.4 percent per year, the equivalent of $77 billion in 2007 dollars, although the actual estimate could vary somewhat depending on the details of the agreement and alternative modelling assumptions. The European Union has said that the United States would gain a comparable amount from T-TIP. Some have described these totals as small, but I think I would risk losing my license to offer economic advice if I counseled anyone to leave $77 billion lying on the sidewalk each year."