Joe point out to me that the subtitle is "Interest Rate Differential Since 2000." That's the key to the chart...differential. Maybe it says something about the chart that I didn't notice the subtitle or that my eyes were drawn to the ranges on both axes, but I made a mistake. Phew, that felt good to say.
Joe recommended recreating the graph that I had previously posted with a single axis range, since the ranges were so close already.
I also wanted to look at the differential, since the author's point was to show that the differential between the Fed funds rate and the 30-year fixed mortgage rate was that the Fed funds rate only influences the 30-year fixed rate. If the Fed established mortgage rates, then the chart would be completely linear, which it clearly is not.
I chose the color red since the farther from the zero axis, the less influence the Fed has on mortgage rates. The darker the red, the less the influence.
I also changed the title so that it would be more clear what the chart was comparing. The author of the article titled the chart "Fed Fund Rate vs. 30-Year Fixed." When I recreated the chart, I simply took the Fed rate and subtracted the 30-year fixed rate, but that made the chart a mirror image of the author's, meaning that he had the title backwards in my opinion, thus the title I arrived at.
The bottom line is that I agree with Dan Green's evidence...the two rates are NOT strongly correlated.