Read "Unequal Democracy: The Political Economy of the New Gilded Age" by Larry Bartels. He gives some evidence of the harmful political effects of income inequ

Read "Unequal Democracy: The Political Economy of the New Gilded Age" by Larry Bartels. He gives some evidence of the harmful political effects of income inequality. I don't know why it matters whether the scale is increasing - I think it's enough to show that it is harmful. It's honestly a pretty boring book, so more work needs to be done on this.