**Live from the Laugher Curve: Bill Easterly**: On Twitter: @bill_easterly: "The Laffer Curve napkin is mathematically incoherent: why is the x variable on the y-axis? Why is 100% at the origin?"

Why does the "normal" range in which d(TR)/dt > 0 extend from a tax rate t of 100% down to 50%? Why does the "prohibited" range in which d(TR)/dt < 0 cover 50%>t>0%?