You're really putting on a clinic.
It's possible to infer rates of change from the different slopes in the chart, but the chart explicitly displays
amounts of change, and not
rates of change. It shows that the annual income of the top 0.1 percent of the income distribution is 324 percent higher than it was in 1979. Said differently, the top 0.1 percent now earns over three times as much as it did in 1979. In contrast, the bottom 90 percent (the vast majority of us) now earn incomes that are only 16 percent higher than they were in 1979. Again, these are amounts, and not rates of change.
Also, please note that the chart does not begin at zero, as you keep insisting. It begins at 100 percent, because it's measuring incomes on an index scale relative to the base year of 1979. The person who created this chart picked that year for a very good reason, as
this chart illustrates:
This shows the share of national income going to those in the top 10 percent of the income distribution. In the three decades after WWII, this measure was remarkably stable. Rich people earned a lot more than poor people, but as national income grew the relative distribution of income stayed the same. The rising tide really did lift all boats.
Right around 1980, that began to change. By 2012, the top 10 percent's share of national income had risen from about a third to over half. This reflects a massive upward redistribution of income. Over the last three or four decades, increases in our national income have flowed almost entirely to the top of the distribution, leaving everyone else with little to show for our increased national prosperity. As my initial chart illustrated, the rising tide now lifts only the yachts.
That is the real story of income inequality in this country. It can't be explained by social dysfunction among poor people or
inadequate education or any of your other pet theories. But you'll make no progress on any of this so long as you can't even sort out how to read a simple chart.