Is there anything wrong with this graph? ; Looking for a good economist

I’m trying extremely hard to stay out of the comentariat concerning education. My love is instruction, not politics. Students, not funding. Engagement, not class sizes.

So with that in mind, let’s take a look at this graph presented by Bill Gates.

Now, I’m not an economist, so can one of you out there that is redraw this graph to include inflation? Is the slope of the line steeper or less steep than the spending line? This is not a trick question, I have no idea. I don’t even really know how to properly quantify inflation even if I knew what it was over the past four decades.

Addendum. I guess I should clarify this first: have these numbers been adjusted for inflation already? Anyone? Bueller?