Crash - focus only on that part of the plot that corresponds to the Reagan years (1981-1988) - it's the only segment that is roughly flat. Percy was only referring to that segment with his characterization of "flat".
Note that the steepest segment of the curve is the very last part - well within the Obama years.
A lot of people in this thread seems to have misconstrued Percy's statement that wealth trickles down. He is basically arguing that the value of the trickle-down economic is similar to a simple equation:
Value = A - B
When he says that trickle-down happens, he is merely stating that A is greater than zero. He says nothing in that moment about B, which is the detrimental aspect of the equation. He has later abundantly demonstrated, that, in his opinion, B > A, so that the total value of trickle-down economic theory is negative.
- xongsmith, 5.7d