In contrast to the last expansion, which ended so dismally, household balance sheets are in much better shape. Household income is five times debt-service costs.
In these circumstances, Sonders explained that most American households would be net beneficiaries of rising interest rates.
Another difference she pointed out was that correlations across asset classes and even within the U.S. stock market itself are crashing. In 2008, every financial asset moved in lockstep.
Today, one can find huge divergences with in industries, from technology to industrials. Just look at Honeywell vs. GE.
Valuation metrics are all over the place. Sonders observed that equity risk premium measures such as the ones the Fed uses say valuations are reasonable, but the Shiller CAPE ratio and Warren Buffett's total stock market value-to-GDP ratio point to a "wildly overvalued" equity market.
Her favorite sentiment indicator, the Ned Davis Crowd Sentiment measure, is well into the extreme optimism zone. When it has reached that level, returns over the next 12 months were negative.
Politics are not swaying markets nearly as much as people think, Sonders said. "I don't know any economist who has ratcheted up GDP forecasts" because of tax reform.
Still, there is a possibility that stocks will keep surging higher over the next 12 months the way they have since mid-2016. If this turns into a frothy melt-up, it would hardly be the first. And experience shows they don't end well.