If the economy goes into recession, earnings forecasts are not 10% to 12% too high. Instead they might be 20% to 40% too high. In other words, if the economy goes into recession, the earnings forecasts are horribly wrong. They might be so wrong that one can make the case that the market might be overvalued. We believe this is part of what is bothering the markets, the epiphany that the economy is much weaker than expected and a recession will blow a hole in earnings forecasts to the point that the market might not be cheap anymore.
---James Bianco via Ritholtz, See link for charts and discussion