Dan Shaviro (NYU; Google Scholar), Ten Observations about Income Inequality:

What is income (or other material) inequality, how should it be measured, and why should tax policymakers care about it? The answers to these questions are contested and ambiguous. With the aim of illuminating the underlying issues, this paper offers ten main observations that might help to inform tax policy debate. It finds that more important than any particular conclusion is the need for continuing methodological pluralism, agnosticism, and humility in how one thinks about it.

Conclusion
There is no simple answer to the question of why (and how much) inequality matters. It inherently presents compound issues, as inequality at different points along the continuum may matter for different reasons that themselves may vary with the broader social context. There also is no simple answer to the question of how inequality should be measured. Perhaps more important than any particular conclusion is the need for continuing methodological pluralism, agnosticism, and humility in how one thinks about it.

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