Comment Re:Aggregate Welfare? (Score 2) 12
They did define it in the actual paper (Eq. (7) on pg. 8). Saying this, however, isn't particularly helpful. They define welfare as (essentially) "Real Wages = Income / Price Index".
I'm not an economist, but from a first read, what I see is that they take some existing simplified trade models which allow exogenous factors (ie, trade patterns *outside* the country in question) and then model it as a globalized system covering a bunch of countries. They model the results across multiple years while holding different sets of variables constant.
Like so many papers, this one appears to be just looking for views. From Fig. 7 (p23), the increase in the relative welfare in the US from 1960 to 2020 is normalized to a change from 0.9956 -> 1.0 (ie, 0.5%).