Very steep yield curve - inflation is likely to accelerate
Inverted yield curve - predicts coming recession
When inversion ends and begins to steep again - economic recovery, great time to buy bonds
- Rob Insana , Message of the Markets
Note: this warning sign may have become surpressed under the Fed's artificial low interest rate policy
stock crashes in a major market becomes contagious
technical (flash crashes)
Many of these events cannot be predicted. These events can happen anywhere in the world. Global markets are now highly correlated. Thus, to avoid these black swans with certainty, you'd have to be out of the market most of the time.
Hence, an investor should stay invested and the safest way to invest is by value investing.