I think it is still relevant and a good indicator of what is to come. Historically, whenever the indicator is above GDP, a crash will follow. case in point, 2000 dot.com bubble burst and 2007 financial crisis. I don't think you should stop investing or dump all stocks now, because no one know when, or if, the market will come crashing now. But it is nevertheless important to be prepared. I'm sticking to DCA. Prices go up, buy. Prices go down, also buy. As long as the stock you invest in is fundamentally good, it'll eventually go up again, and probably higher....