Dr. Anne Bradley, in Why Does Income Inequality Exist? An Economic and Biblical Explanation, says we should care about income mobility, not income inequality. I think we should care about, and work to reduce, income inequality (along with income mobility) to the extent such inequality is attributable to unjust causes.
What might those unjust causes be?
The answer is probably very broad. For now, let’s stick just to examples Dr. Bradley cites: “not letting business fail when they deserve to fail (bailouts); protecting some businesses from competition (subsidies and tariffs); or letting some businesses succeed over others through protective legislations (licensing and other regulatory requirements).”
What do these — i.e., bailouts, subsidies and tariffs, and licensing and other regulatory requirements — have in common? They are results of government actions authorized by legislation that came out of the political process. What is this political process? Elections and lobbying, to grossly oversimplify. Is this political process always unjust? Hard to say in such a blanket fashion. Is this political process sometimes unjust when viewed from the Biblical standard of justice? I believe so (but admit answering this thoroughly would take a book or two or three…).
So I draw this conclusion, using Dr. Bradley’s terminology: to the extent income inequality results, not from the mere, providential, distribution of diverse gifts, but from “rent-seeking behavior” enabled by legislation birthed through the political process that operates at times unjustly, we should recognize such inequality as “a sign of injustice” and work to reduce it.