How Robinhood Is Changing Stock Investing

When individual-investor communities, not institutions, drive security pricing

John Rekenthaler 6 April, 2021 | 1:11AM
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Not Fully Convincing

Last summer, when I puzzled over the reasons behind the U.S. stock market’s spectacular recovery--which struck me as premature, given that the economy was in a deep recession, with no signs that the coronavirus would be eradicated anytime soon--several readers proposed the following:

  1. The government had flooded the system with cash.
  2. This cash had not only supported asset prices, but had also fueled investment speculation.
  3. This speculation came from retail investors, who were feeling flush, because they had cut their spending while maintaining their income.

I was dubious. For the most part, I adhere to conventional finance theory, which emphasizes rationality. It was not that investors had behaved rashly. Rather, I had failed, by being too slow to recognize the impending economic recovery. Also, the rally was global, meaning that U.S.-centric explanations were not sufficient.

A Kernel of Truth

That said, the readers had a point; the significance of today’s retail investors should not be dismissed. As demonstrated by the GameStop saga, they don’t necessarily operate according to academic rules, and their clout is increasing. This makes for a different stock market environment, with corresponding lessons.

Recently, two researchers for the Swiss Finance Institute, Philippe van der Beck and Coralie Jaunin, supported this contention. In “The Equity Market Implications of the Retail Investment Boom,” the duo finds that Robinhood’s clients contributed handsomely to the second-quarter 2020 U.S. rally, especially for smaller-company shares.

The authors used a (now-dormant) website called Robintrack to measure the activity of Robinhood’s customers. The site provided the number of Robinhood accounts that held each stock, updated several times daily, throughout the second quarter of 2020. Although Robintrack did not provide the account sizes, the authors roughly knew the amount of assets that Robinhood controlled, and thus were able to “reverse-engineer” (better translated as “guesstimate”) how demand from Robinhood’s customers increased for each stock during the second quarter.

(In addition to tracking the activities of Robinhood investors, the authors cataloged various institutional shareholders, such as hedge funds, banks, pension funds, investment advisors, and insurance companies. They used such information to derive an estimate of each stock’s price elasticity, which, in turn, affected their estimate of how Robinhood’s trades affected that stock’s price.)

A Skeptic’s Reaction

It is an imprecise process, in many ways, which leads me to discount the authors’ estimates. They calculate that demand from Robinhood clients boosted the value of the overall U.S. stock market by 1% during the second quarter. This came after their actions had added 0.6% to U.S. stocks’ first-quarter results. Those figures are high. If annualized, they imply that Robinhood’s trades contributed 3 percentage points to the Wilshire 5000 Index’s total return in 2020. That seems … optimistic.

So, too, does the authors’ claim that “Robinhood demand accounted for 20% of the aggregate market capitalization of the [smallest 20% of stocks in the U.S. market].” No doubt Robinhood’s customers punch above their weight, but given that they control only roughly 0.2% of U.S. equity assets, it’s hard to believe they exert that much influence over one fifth of the nation’s publicly listed stocks.

(Then again, Robintrack omitted Robinhood’s options transactions, which also affect stock prices. In that respect, the authors’ estimates are conservative.)

But such quibbles belong elsewhere. The point is that, however cautiously one treats the authors’ estimates, something remains.

Looking Ahead

This trend figures to extend. Small-company index funds continue to gain market share from their actively run rivals, meaning that fewer small-company shares are held by active investment professionals. It therefore seems that individual buyers and not portfolio managers will increasingly be tasked with pricing small-company stocks. The “Robinhoodization” of secondary stocks looks to be in its early stage.

One should not exaggerate the current effect, but the phenomenon must be taken into consideration. The expanding influence of retail stock investors induces behavior that confounds traditional expectations, and it doesn’t appear to be going away anytime soon.


  1. Small-company stocks will act ever more erratically: Perhaps "erratically" is pejorative, but the adverb strikes me as accurate. I don’t know how else to describe the performance of Robinhood favourites, which frequently experience dramatic price changes without corresponding corporate news. Small stocks will march ever more loudly to their own drummer.
  2. Small-company stocks will be better portfolio diversifiers: Different behaviour means lower correlations
  3. Regulatory scrutiny will increase

But what if retail investors are colluding on message boards, pooling their resources with the express purpose of altering security prices? The regulators will not and should not ignore those activities. What is good for the goose will be good for the gander. Along with greater investor power will come the call for greater investor responsibility.


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About Author

John Rekenthaler

John Rekenthaler  is Vice President of Research for Morningstar. Rekenthaler previously served as president of Morningstar Associates, LLC, a registered investment advisor and wholly owned subsidiary of Morningstar, Inc. During his tenure, he has also led the company’s retirement advice business, building it from a start-up operation to one of the largest independent advice and guidance providers in the retirement industry. He currently writes regular columns for Morningstar.

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