The S&P 500 just posted a third quarter of year-over-year earnings growth. But in the shadow of the rebound is a trend that has been worsening for more than two years: a rising number of profitless companies.

About 10 percent of stocks in the benchmark gauge have posted losses in the last 12 months, an uncharacteristically large portion that has no precedent since 2010, according to data compiled by Bloomberg.

What's to blame? Energy companies are a culprit, unsurprisingly. Of bigger concern are technology and consumer stocks that have crept onto the list. Overall, the 51 companies lost $55 billion in the past year. When the market peaked in 2007, the figure was $22 billion.

"It's unusual this far into an expansion that large-cap companies are losing money," said Tom Lee, co-founder and head of research at Fundstrat Global Advisors in New York. "Some of these industries are in trouble. But it does speak to how the economy isn't growing fast enough to create universal winners."

Trailing 12-month earnings in the S&P 500 total about $986 billion, or $113 a share, just below an all-time high reached in 2014. Take out the companies losing money and the total hits $1.04 trillion, or $117, the highest ever.

The aggregate number is nothing to sneeze at. Earnings as a whole are in the midst of a three-quarter rebound in which both sales and profits have grown, and total earnings are poised to climb to $130 a share by year-end, according to analyst estimates compiled by Bloomberg.

But while $4-a-share profits across 51 companies might not scream bear market, it doesn't exactly comport with bull market standards either.

Among those shares, 23 are energy stocks. That leaves $21 billion in losses among the other industry groups. While tech shares weren't the biggest losers by dollar amount, they do make up some of the notable cash-burners. Think Yahoo Inc.

Investors' perception of unprofitable companies varies greatly by industry. While the shares of the money-losing energy stocks have taken a beating, tech shares without earnings are up an average 32 percent in the last year.

Higher share prices on unprofitable stocks may be tied to investors' rush to growth companies this year. However, the companies are weighing on the S&P 500's performance. The median year-to-date move in shares of companies without profits is 7.3 percent, compared with a 9 percent climb in the S&P 500.

Renick writes for Bloomberg News.