I came up with quite an interesting graph today. Below you can see, in blue, the line graph of the SPY over about the past half-decade. On the same graph, in black, is the 10-year note interest rate.
Notice how, until about the April peak, these two tracked each other quite closely. There were occasions when the SPY had to "catch up" with the movement in interest rates, but it always did manage to catch up.
But look at that big, honkin' red arrow I've drawn. There is a huge discrepancy between interest rates (which continue to plunge) and the equity markets (which continue to soar).
My opinion? This is an unsustainable situation. This spread hasn't persisted in the past, and I don't think it will persist into the future.