Planet Money has an interesting post regarding income inequality.  From the 1930’s through the 1970’s only the bottom 90% of wage earners saw their incomes rise.  High marginal tax rates certainly contributed to possible lack of increase in the high wage earners.

Something interested happened in the 1980’s and beyond: Only the top 10% of income earners have seen an increase in income.  We can go back and forth about what has caused/contributed to this.  That is not the question.

The question I have is how sustainable is this?  How much longer can the majority of people in America not see any income/social mobility upward before civil society starts to unravel.  It is not hard, or deleterious to the top 10% for the bottom 90% to have income mobility.  They will not starve. They will still have more wealth than they can use for whatever purpose they want.  They will not go hungry, or homeless.