it actually does change. both lines are approaching infinity (asymptote), which means the slope will be so high they will look like vertical lines, meaning there won't be a "top" line, because its next to the other one, making the "gap" infinity large as well.

Yeah Nero, and you Adobe Reader, and 90% of all commercial antiviruses, we're all looking at you.

The funny thing about that comic strip was the second part – the one which author of this post cut off. Way to go. >.>

what part is cut off?

check the source link.

The graph is wrong.

The lines indicates the productivity gap is widening as time goes on.

I'm a nerd aren't I?

Its not.

The productivity is vertical (as shown by the tiny arrows)

So it doesn't change

it actually does change. both lines are approaching infinity (asymptote), which means the slope will be so high they will look like vertical lines, meaning there won't be a "top" line, because its next to the other one, making the "gap" infinity large as well.

You are wrong. The curves are not asymptotic. They are parabolas. The vertical gap between y=x^2+1 and y=x^2+2 is always 1.