Just a remarkably simplistic (and convenient for his day job) column here from @porszag, arguing that if rising industrial concentration is caused by superior productivity rather than lax antitrust enforcement, we shouldn't worry about it. bloomberg.com/opinion/articl…
I have no reason to doubt the study it’s based on, which is by some of the most eminent economists working today (putting aside that the only major differences between the 2017 version and the update are this new productivity explanation and a handful of corporate funders)
But there are two pieces of the new version that complicate Orszag’s narrative. One is that very small differences in productivity may confer huge gains upon superstar firms, which would square with the fact that overall productivity growth has been so sluggish. 
Another is that the productivity story and the enforcement story aren’t mutually exclusive — the authors explicitly don’t rule out that superstar firms may be locking in their advantage through lobbying, etc.
Finally, regardless of how firms become superstars, the problems associated with their increasing dominance of the economy remain. There are plenty of other ways to boost productivity — education, infrastructure, federal research $$ — without giving in to monopolization.
I understand that more aggressive antitrust enforcement is bad news for investment bankers who make a lot of money on M&A. But that's no reason to write a lazy column that will nevertheless shape elite opinion more than a thousand other studies that paint a more nuanced picture.
