It's hard to objectively calculate how large the impact from corona virus will be and how it has affected the supply chain. Additionally, this could be a black swan event that could become a catalyst, this is not an isolated event and it will send a shockwave across the markets.

The losses in earnings as well as the reduction of consumption are hard to estimate, they need to be priced in into the stock's price which might be currently undervalued or overvalued. The idea is that no one knows exactly what the prices should look like. You might go for the S&P yield and end up losing 20% in the short term because of the price tanking.

The point is that investors like certainty, that's why some are holding cash or even a mix of bonds, cash and gold. They might prefer lower yields than S&P and more certainty.