[popra]

Haven't read the full paper but is seems to suggest that returns on capital investments are declining because of consolidations. Companies in dominant positions make huge profits(compared to the rest of the players), while those that are not in dominant positions make far less profit - but on average the returns on investment are on the decline. Furthermore the huge profits deincentivise risk taking for the dominants, hence they invest less. But not being an economist, I may be way off.