We can use that level of about 23 times earnings as a benchmark for measuring the length of time between bubble periods where investors disregard risk aversion. (hussman.net)
As I've often noted, nothing in the historical data encourages the attempt to speculate in a bubble once extremely overvalued, overbought, overbullish features emerge - and nothing in the historical record, even considering prior bubble periods, indicates we should speculate here. (hussmanfunds.com)
In recent years statistical tests have been developed to locate mildly explosive bubble periods... (sr-sv.com)