At what level of abnormal undervaluation of equity markets has a correction started in the past?

Equity valuation in the United States and the euro zone is becoming abnormally low, while companies' financial situation remains very positive. At a certain level of undervaluation, the equity market must therefore rise again. We seek to determine when this configuration has already been seen in the past, and at what abnormally low valuation level a correction started. When the PER falls to 14-15 in the United States and 11-12 in the euro zone, when the equity risk premium reaches around 6%, the undervaluation of equities relative to the fundamentals corrected in the past and the equity market picked up again. We are currently in this zone.