1. Ex ante perceived safe – ex post turns out safe - "Just what we thought!"
2. Ex ante perceived risky – ex post turns out safe - "What a pleasant surprise! That's why I am a good banker"
3. Ex ante perceived risky – ex post turns out risky - "That's why we only lent little and at high rates to it."
4. Ex ante perceived safe – ex post turns out risky - "Now what do we do? Call the Fed for a new QE?"
Because, as I see it, from this perspective, your 20% risk weights for the dangerous AAA rated, and 150% for the so innocous below BB- sounds as loony as it gets.
Here are some of my current explanations of why I believe the risk weighted capital requirements for banks are totally wrong.
And below an old homemade youtube, published September 2010, on this precise four scenarios issue