Unless something goes spectacularly wrong, the assets under management at U.S. listed Exchange Traded Funds will surpass $2 trillion for the first time this month. No, this capital does not explain why U.S. equities sit near all-time highs. Redemptions out of U.S. stock mutual funds over the last five years total $411.1 billion and domestic equity ETF inflows are just $301.5 billion over the same period. And you can’t pin low interest rates on ETFs either – 5 year flows into fixed income products total just $132.5 billion, as compared to the $814.3 billion from mutual funds investors. So why are ETFs important? For investors and traders, they are useful “Tells” of market psychology. Those involuntary twitches point to a U.S. stock rally through year end, for ETF inflows are 2x mutual fund outflows. And for market professionals – brokers and money managers alike – ETFs are a reminder that “disruptive technology” isn’t just for Silicon Valley. It happens in our business as well.