Not even.:D
Figure if the arm moves 1/2 inch then the tip of the wiper blade moves probably 6 inches.
Try moving the wiper itself from one end of it's travel to the other and measure how much the arm under the dash travels from one end of the travel to the other.
That should give you an idea of where to start.
Just a thought, is it possible your main arm from one wiper assy to the other is on the wrong pivot?
I can't imagine why the ratio between the two wipers would be different if the rod is on the correct pivot pin.