PremiumAuthored by Peter Berezin, Chief Global Strategist at BCA Research,Bubbles in E, Not in P/EMost stock market bubbles feature an unsustainable increase in share prices in relation to earnings. That was certainly the case during the dotcom bubble when the growth in earnings was dwarfed by the rise in share prices. Sometimes, however, an unsustainable increase in earnings is the source of the bubble.