In 3 Ne 6:10-14, the prophet Mormon attributes the downfall of the Nephite people to “a great inequality in all the land.”
In his 2012 book, Coming Apart, Charles Murray describes the increasing gap of values and lifestyle choices between the upper and lower classes in the US. As a Libertarian, Murray does not see the changes driven by economic inequality. See my take on his book here.
Decades of research have led sociologist Richard Wilkinson to the same conclusion as Mormon. Inequality rather than income make the difference in how well societies function. Check out his TED talk here.