Here are a couple of interesting ones. Several more are at the link. Many of these raise as many questions as they answer.
I think these two charts point to the strong role of female empowerment in the shape of incomes over the past 40 years. I linked to an interesting paper about that (here).
- Since the early 1970's, most of the gains have gone to high income households.
- Since the early 1970's, most of the gains have gone to women.
Both of these things are true. In fact, they are both probably largely describing the same phenomenon.
Unfortunately, the first version is both more rhetorically exciting and more likely to lead to poor policy choices than the second version.
There are a host of factors feeding these income trends. The technology boom has fed the tremendous income gains at the very top. (I've seen somewhere, but I don't have the link handy, that the entire climb in inequality over the past few decades goes away if you exclude a handful of counties around Seattle and San Francisco.) (Edit: if this is the paper I was remembering, then my counties are slightly off -NY instead of Seattle- and I have somewhat overstated the effect. These counties explain most inequality during the dot Com boom of the late 1990s.) But, also, as referenced above, we can also explain all of the growth in inequality with the changing incomes of women within households. We can also explain some of it with changing lifecycles and demographics (more low income students in early adulthood and more low income retired households). We can also explain some of it with housing. Imputed rent is not included in household income, and this is becoming a larger portion of the median household's true income.
So, it looks like inequality is explained many times over. I don't think this is an error. I think all of these things are legitimate explanations. The counterbalance is that a rising tide lifts all boats. These factors have all been balanced out by the natural equalizing tendency of capitalist markets and the tendency of economies with rising incomes to expand their social safety nets.
We can lower measured household inequality by supporting undistorted free markets, halting the technology boom, reversing the empowerment of women, replacing support for post-secondary education with support aimed at other forms of human capital development, reducing incentives for overinvestment in housing, or increasing the social safety net. The low hanging fruit here includes the removal of barriers to entry (technology is doing some of this, reversing things like occupational licensing would help also), transformation of education subsidies, and housing policy. These aren't necessarily political feasible, but they would be helpful.
The continuation of the technology boom and empowerment of women are clearly far more important than the issue of income inequality. This is one of many reasons why poverty is a much more coherent issue to focus on than inequality. Feminine and technological advances are clearly beneficial, even while making measures of inequality worse. We wouldn't even think of reversing course on these issues in order to reduce inequality. That is because inequality is not, legitimately, a concern, so it tends to conceptually collapse in the absence of strawmen and boogeymen.
If someone is concerned about inequality when thinking of CEO's or hedge fund managers, but he isn't so concerned about it when thinking about households of married physicians or married lawyers, then he is really just pretending that his bitter attitude toward CEO's and hedge fund managers is a concern about poverty. This is especially egregious in moralistic complaints about globalization as a cause of income inequality, where corporations and developing economy workers have joined together in an equalizing revolution of global economic improvement.
How about the concern that the internet and pirating are preventing musicians from capturing income from their recorded music. Is there a group of people with a more extreme level of income inequality than popular musicians? Why do we bemoan their falling incomes, but cheer for moderation of CEO and financier incomes?
The inequality meme joins a long list of rhetorical emblems that have served to seemingly transform being against something into being for something. These rarely serve the greater good. If something is worth being against, then it's worth being against. The use of the rhetorical device is, itself, a sign of weak moral backing.