Yelnick writes:

An interesting correlation since the Global Financial Crisis has been AUD and the S&P.

The more specific correlation is that QE drives up commodities, something also predicted here, and therefore commodity currencies like the AUD. Australia, however, is now in a bind, as its currency is over-valued for its value-added industries, and its mining exports are suffering due to the Chinese slowdown that may yet turn into a hard landing. Indeed, the AUD correlation broke over the past nine months as China began to slow.

Yelnick says that "rather than call the top, we should watch the divergence."