Hendrik Bessembinder's research has a habit of detonating quietly in academic circles before the shockwaves reach everyone else. His latest study, published in March 2026, is no exception. The Arizona State professor has spent years documenting the extreme skewness of stock market returns. The uncomfortable truth that most stocks fail, and a tiny handful of winners carry the entire market. His new findings suggest this concentration is not just persisting. It is accelerating.
The numbers are striking. From 1926 to 2016, 89 firms accounted for half of all wealth created on the US sharemarket. In the decade since, just 46 firms have done the same job. In other words, the number of companies doing half the market's heavy lifting was cut nearly in half in a single decade. The names behind that shrinking list will surprise nobody who has watched markets over the past ten years: the mega-cap technology and platform companies that dominate markets and news cycles alike.
What is more unsettling is what this implies for everything else listed on an exchange. The median listed stock survives just seven years before being delisted, wound up, or absorbed by an acquirer. Over that brief life, it delivers a total return of negative seven per cent. Materially worse than simply holding US Treasury bonds and doing nothing. For many businesses, Bessembinder's data implies that the public market has become less a venue for growth and more a mechanism for exit. A place founders and early backers go when private funding dries up and they need liquidity. When companies list for the wrong reasons, they tend to struggle. The median stock's dismal lifetime return is the data confirming what many investors already sense.
The broader picture
Markets mirror society and may be helping drive inequality
The finding lands with force given the broader economic backdrop. The so called K-shaped recovery. In which higher income households have pulled further ahead while others have stagnated. Has been a defining feature of the post pandemic economy. Bessembinder's work suggests the stock market is not merely reflecting that dynamic. Given how much global household wealth is tied to equity ownership, the extreme concentration of market gains may be actively reinforcing it. Because equity ownership is itself skewed toward wealthier households, the narrowing of returns into a smaller number of very large winners amplifies wealth gaps that already exist.
There is also a fascinating tension with one of the most durable ideas in finance: the small-cap premium. The long held academic belief that smaller companies inherently outperform larger ones over time has underpinned entire categories of index funds and ETFs. Bessembinder's data puts that thesis under severe strain. One likely culprit is the shift in competition law over the past two decades. Big Tech's playbook has been acquisitions. Google absorbed YouTube, Facebook bought Instagram, Amazon expanded aggressively into new retail categories. By buying potential competitors before they mature, platform giants have effectively captured the growth that previously flowed through smaller listed companies, cannibalising the small-cap premium before those businesses ever get the chance to outperform independently.
What it means for investors
Three uncomfortable lessons
The first is to rethink small-cap allocations. An allocation to something like the Russell 2000 is increasingly a pledge to own the median stock. The one returning negative seven per cent over its life. The premium, if it ever existed, appears to have collapsed.
The second is that the value premium may be structurally impaired. If the momentum effect is as persistent as Bessembinder's century of data implies. The winners keep winning and losers keep losing, then the classic value strategy of buying cheap, unloved stocks and waiting for a reversion may be waiting in vain. Companies that have fallen out of favour and stopped generating returns may do so permanently, not temporarily.
The third, and most counterintuitive for passive investing, is that not all diversification is created equal. Spreading capital thinly across hundreds of companies means owning a great many losers in exchange for a handful of winners. What Bessembinder's century of data rewards, in retrospect, is concentration in companies that had already demonstrated they had won their markets; mature, high quality businesses with durable competitive positions. Not speculative listings chasing a private market style exit at the public's expense.
None of this means the market has stopped working. It means it has become more ruthlessly, a winner take all. For investors willing to accept that framing, the lesson is not to despair but to recalibrate. Fewer, better, bigger and a great deal more scepticism about the next IPO that arrives with a compelling story and a recent fundraising round.
