In practice, "black swan" is supposed to mean effects which we underestimate or fail to predict at all. The definition requires not just rarity but an event whi

In practice, "black swan" is supposed to mean effects which we underestimate or fail to predict at all. The definition requires not just rarity but an event which hasn't been seen before, and is only only understood in retrospect. You can try to leave a general hedge for unknowns, like never giving anything >99% long term confidence. But actually pricing black swan problems accurately should be impossible, pretty much by definition.