There have been two main reasons when VNQ has outperformed SPY.
1. When Real Estate was the hottest thing since sliced bread
2. When SPY Has gone into a sideways or down market
With Real Estate prices being hot while commercial beaten up
VNQ net has out gains but subpar to SPY. That seems to be changing
based on this ratio setup. I venture to say it will likely be due to SPY
getting tired.