We need to look at other possible explanations than trade
Bhagwati would serve his worthy cause better by pointing out the effects of other developments that have run in parallel to the growth of global trade. How much of the capital-labour gap could be explained by the following?
1. The discrimination implicit in risk based pricing that has allowed the financial sector to charge some groups with extremely high interest, based on some quite dubious logical reasons. Borrowers that cannot pay the high interests should not have received the loans to begin with, at least not at those high rates, and those who can serve the loans have de-facto evidenced they merited lower rates.
2. The growing tendency to use intellectual property rights of all sort and kinds to create unregulated monopolies that capture rents.
3. The increased regressiveness of taxes that results from the tendency of turning away from taxing income to taxing consumption.
Net out the effect of those three factors and you might not have anything left to blame trade with.