QE is unprecedented. If you look at the absolute yields, we're talking about rates below inflation (1.8%). It's an inversion but the magnitude is so low it's hard to compare it to past inversions. Equity valuations are pretty much in line with earnings with the S&P 500 index as a whole trading around 20x earnings. Considering how low the risk free rate is (US treasuries), that's not a booming valuation and is probably undervalued if interest rates stay this low considering most of these companies return at least 10% on tangible equity. Unemployment is low right now, but so are wages and so is inflation so it's not like we're booming there either.