David Park at The Monkey Cage points to an article by Maria Petrova on a model of democracy where the rich bribe the media into misinforming The Poor about the costs and benefits of redistribution so that The Poor favor less redistribution than they would otherwise (link to paper). Petrova’s theory is seriously flawed because she inappropriately uses self-interest as a group motivation. Petrova writes (italics mine):

Unequal societies may have a low level of redistribution because the median voter may misperceive her self-interest as a result of an information campaign by the rich. Higher inequality in the economy implies more incentive for the rich to manipulate the preferences of voters and to use the power of the media to advocate a lower level of taxation. The influence of the rich on the media is one reason why income inequality leads to political inequality, and why policy outcomes are more responsive to the preferences of the rich than to those of the poor.

Petrova abuses the word ‘incentive’ here. The word ‘incentive’ is generally used to refer to individual incentives, or at least incentives for social units that act largely as single entities such as individual corporations, and to use it to mean something else at best poor word choice. ‘The Rich’ is a class of people, not an individual person, and to assume that The Rich act as a cohesive unit, without at least attempting to provide an explanation for why this would be so or providing solid evidence that it is so, is appallingly bad social science; the theory of groups demolishes any presumption of such solidarity, especially when, as Petrova explicitly assumes, group action requires that people bear real costs. This assumption on page 7, for example, cries out for an explanation

The rich can offer a bribe to the newspaper [the media in her model]. I assume that the members of the high-income group divide expenditures on this bribe equally. (p. 7)

Petrova never discusses how The Rich are able to coordinate their bribe or how they are able to enforce cost sharing, and it seems unlikely that they would be able to do so.
The only place where Petrova seems aware of fact that The Rich is a set of individuals with their own calculus is in her conclusion when she notes ways in which her model might be extended:

Then, not all the rich can be organized as a group attempting to influence the media; some of them might stand aside.

But this seems more like splitting The Rich into two cohesive units than recognizing that The Rich have individual incentives.

I do not mean to say that effects which encourage collective action cannot not exist; they could; perhaps institutional arrangements or human psychology encourage the Rich to act in their collective self-interest (I would actually be extremely interested in explanations focusing on psychology, especially those grounded in empirics), but such explanations are essential to her theory and would clearly be controversial, so neglecting to discuss them is a serious oversight.

I will probably be posting about the overuse of ‘self interest’ in positive theories about politics more frequently in the future.