So long as volatility is falling, I conjecture that it must be statistically profitable arbitrage to short the S&P and go long on the proceeds with the Russell 2000.  I expect to see this behavior especially today, given the continued small cap run in the short term and the selloff yesterday.

    Feel free to call me out on this if the VIX continues to fall but the Russell does not return above the S&P, despite the continued large cap M&A today.