Understanding a stock's historical trends is smart, especially if it's based in a cyclical industry like Alphabet (GOOG 1.16%) (GOOGL 1.32%). Most of Alphabet's revenue comes from advertising, which can rise and fall alongside economic expectations. While the economic outlook is uncertain, there is more to Alphabet's rapid price decline this time.Alphabet's stock now trades for around 17 times trailing earnings, a level it last reached only three times: 2008, 2012, and 2022. This is the company's fourth tri ...