Beneath the glow of stock-market records, darkly bearish trends are lurking

Market breadth, a measure of how many stocks are rising versus the number that are dropping, has turned “exceedingly negative,” according to Brad Lamensdorf, a portfolio manager at Ranger Alternative Management. Lamensdorf writes the Lamensdorf Market Timing Report newsletter and runs the AdvisorShares Ranger Equity Bear ETF HDGE, +0.47% an exchange-traded fund that “shorts” stocks, or bets that they will fall.

“As the indexes continue to produce a series of higher highs, subsurface conditions are painting an entirely different picture,” Lamensdorf wrote in the latest edition of the newsletter. He noted that the year-to-date advance in equities — the S&P 500 SPX, +0.19% is up 10.6% in 2017 — has been driven by outsize gains in some of the market’s biggest names.