As it happens, there hasn't been a lot of research on the distributional effects of greater competition: a big survey last year done by European Commission staff, 'Ex-post economic evaluation of competition policy enforcement: A review of the literature' found (p29) that
But as luck would have it, along comes some new research, 'Competition policy and inclusive growth', which has had a crack at looking at the distributional impact of increasing competition (through the various effects of the European Union's policies against anti-competitive mergers and cartels). Their bottom line is that "Interventions have important redistributive effects that benefit the poorest in society", and here are some of the key numbers. The model captures the eventual economy-wide effect of a 'mark-up' shock (a setback to producers' profit margins from competition enforcement) on different groups in society.When a lack of competition raises prices and reduces the quality of products, it causes damages to all consumers, including the poorest people. In this context, it could be interesting to analyse the distributional effects of market power. Existing evidence seems to suggest that an increase in competition is particularly beneficial for low-income people. However, the literature in this area remains in its infancy and there are a number of topics deserving further research.
You can see that there are more jobs, and higher wages, for rich and poor alike, but poorer households' consumer spending goes up a good deal more than rich households' (because poorer households of necessity save less). And the rich unambiguously lose through the reduced profitability of the companies they, as the shareholding class, own.
I wouldn't necessarily go mad about this: these are early days for this kind of research, and the type of DSGE model used, while the bee's knees in modern modelling circles, can be a finicky hothouse contraption. But the results are exactly what you'd have expected: rolling back anti-competitive market power is good for consumers, and for poorer consumers more than richer. I'd draw an analogy with the producer market power created by protectionism: the poorer are disproportionately affected by the higher prices of the things that are typically 'protected' most (food, clothes, shoes). And it stands to reason that the poorer will be worst hit by any anti-consumer development: they had the least choice to begin with, whereas the rich have more options.
In any event we should know a bit more in the near future: this work was part of a conference the World Bank ran last year on 'Promoting Effective Competition Policies for Shared Prosperity and Inclusive Growth', and there's apparently a conference volume on its way.
Finally a hat-tip to the Vox website, the policy portal of the Centre for Economic Policy Research, which published these results. It's a terrific compendium of timely, wide-ranging, practical research, with something to say (in readable, short format) on all the important issues of the day. Highly recommended.