The unusual behavior of the federal funds and 10-year Treasury rates: a conundrum or Goodhart’s Law?

In February 2005, former Chairman Alan Greenspan referred to the decline in long-term rates in the wake of the Fed increasing the target for the federal funds rate by 150 basis points as a “conundrum.” Greenspan’s remarks generated considerable interest and research. I show that the relationship between the 10 year Treasury yield and the federal funds rate changed dramatically in the late 1980s, well in advance of Greenspan’s observation. I argue that the marked change in the relationship between the federal funds rate and long-term yields is a natural consequence of Goodhart’s Law.