Q: What do we care about?

A: Per-capita GDP
http://www.brookings.edu/research/interactives/2013/income-well-being

The EU's new happiness indicator, billed as being so much more relevant to modern governance than GDP, measures happiness probably not as well as GDP/capita, but much better than income inequality
http://prcweb.co.uk/lab/what-makes-us-happy/

Q: How do we get more GDP/capita?

A: By increasing GDP. First by increasing it faster than the population can grow, which stabilizes the population, then at any rate thereafter
Macroeconomic Regimes

Q: What about inequality?

A: Historically, the only thing that has decreased inequality is GDP growth. This is true for all historical timescales, including the postwar era
Gapminder: per-capita GDP vs top income decile
Gapminder: per-capita GDP vs Gini index

Peter Norvig's "economics simulation" suggests that rising economic inequality may be inevitable in a zero-sum economy
https://github.com/norvig/pytudes/blob/main/ipynb/Economics.ipynb

In the United States, income inequality wasn't a mainstream issue prior to 2009, when GDP growth slowed.

Global inequality has lately fallen at a historically unprecedented rate, thanks to historically unprecedented GDP growth in Asia and Africa
Parametric Estimations of the World Distribution of Income