Monday's action in US equities was much like a duck floating on a pond. Up top, nothing much seems to be going on. The Dow (up 14 basis points), the S&P 500 (down 1 basis point) and the NASDAQ (down 19 basis points) all behaved like coming to work was the proverbial waste of a clean shirt.

But, below the surface, there was a lot of action. We had several client emails on this after the close, calling dramatic out moves like:

The Russell 2000: up 1.3%. US small caps have been laggards all year, but Monday's move closed the YTD performance gap by 20%.

Large cap Financials: up 1.5%. One of the more-troubled groups in the S&P 500 this year, but Monday's performance cut their YTD lag by 44%.

US Momentum stocks (using the MTUM ETF as a proxy): down 1.7%. Monday's move cut the YTD outperformance of this style versus the S&P 500 from 357 bp to 186 bp, a 48% decline.

US Min Vol stocks (using the USMV ETF): down 0.9%. Like Momentum, this has been a winning approach in 2019 but Monday's drop sliced 20% off its YTD outperformance (448 bp Friday, 363 Monday).