Do stocks beat the rest once an activist investor's 13D is public?
No. Since 1995, US stocks with an activist 13D stake made public in the previous 90 days beat the same day's median stock over the next month 49 times in 100, and over three months 50; a coin flip gives 50. Over the next session and week they leaned slightly below 50: faint, not reliable on its own. Ranking by activists' share of large holders showed no measurable edge either.
The paper
The full study: its data, method, robustness, limits and sources.
Opulence Alpha Research · Published Sep 25, 2026 · Data through Aug 21, 2026
Keywords: activist investor stocks, 13D filing stock returns, does following activist investors work, hedge fund activism returns, activist stake, 13D filing·JEL classification: G11, G12, G14, C12, C58
- Universe
- The same for every study: 1,767 US common stocks in the 11 GICS sectors, 422 of them since delisted; S&P 500 members since 1996 plus large and mid-sized companies outside the index
- Period
- Every Wednesday from Jan 4, 1995 to Aug 19, 2026: 1,634 Wednesdays across 7,959 trading sessions
- Sample
- n = 1,763 stocks of the 1,767-stock universe; 1,889,758 stock-weeks, a median of 1,148 stocks per Wednesday
- Outcome
- Return over the next 1, 5, 21 and 63 trading sessions against the same day's median stock
- Inference
- t on non-overlapping dates; proven only when |t| ≥ 3 and the same sign in at least 60% of years
1Introduction
When an investor files a Schedule 13D, it discloses a stake of more than five percent in a company and an intention to influence how the company is run. Forums and the financial press often treat these filings as a lead to follow: if a well-known activist is in, the stock should do well. Academic work finds that prices react around the filing itself (Brav, Jiang, Partnoy and Thomas 2008). This study asks the question a reader of the filing faces: once the stake is public, do those stocks go on to beat other stocks?
2Data and method
2.1Sample design
Population and frame. The population is US common stocks listed on the NYSE and Nasdaq; funds, ETFs, trusts, preferred shares, warrants and units are excluded. The sampling frame is a fixed universe of 1,767 companies, drawn once when the platform was built and not re-sampled since, in two strata. Stratum 1 is a census of the S&P 500: every company in the index at any time since 1996 whose price history could be recovered, 1,027 companies of which 413 have since delisted; it holds 76% of the index's members in 1996 and at least 96% in every year from 2010. Stratum 2 is 740 large and mid-sized companies outside the index, selected in proportion to the market's sector weights from the stocks that passed a minimum share price of $15 and a minimum average daily trading value of $25 million; 9 of them have since delisted.
Sample. The unit of observation is a stock-week: one stock on one Wednesday. A stock enters a Wednesday's cross-section when it has a valid close that day, a value of the signal and a measured outcome; bars flagged as bad data and returns that cross a change of issuer are left out. This study's sample is n = 1,763 stocks of the 1,767: 1,889,758 stock-weeks on 1,634 Wednesdays from Jan 4, 1995 to Aug 19, 2026, a median of 1,148 stocks per Wednesday (range 820 to 1,371). 331,954 stock-weeks (17.6%) come from the 422 companies that have since delisted. Every stock and every Wednesday carries equal weight.
Representativeness. Table 1 gives the sample by GICS sector beside the S&P Composite 1500: 7.9% of companies would have to change sector for the two to match exactly. By latest market value, 55% of the active companies are large (at least $10bn), 38% mid ($2–10bn) and 6% small. Because Stratum 2 was chosen from companies listed at construction, its history carries survivorship bias. Section 4 repeats the lead result among the stocks that were S&P 500 members on each date, the part of the sample largely free of that bias.
Companies in this study's sample, of them those since delisted, the size of the active companies, the sample's share of stock-weeks and the sector's share of the S&P Composite 1500.
| Sector | Sample | Delisted | Large | Mid | Small | Stock-weeks | S&P 1500 |
|---|---|---|---|---|---|---|---|
| Information Technology | 282 | 67 | 122 | 76 | 18 | 13.9% | 12.7% |
| Financials | 256 | 60 | 114 | 74 | 8 | 14.6% | 17.2% |
| Industrials | 255 | 53 | 126 | 67 | 11 | 15.9% | 17.5% |
| Health Care | 237 | 47 | 92 | 81 | 16 | 12.4% | 10.9% |
| Consumer Discretionary | 209 | 39 | 69 | 87 | 12 | 12.3% | 12.9% |
| Energy | 105 | 30 | 39 | 31 | 5 | 5.9% | 4.7% |
| Consumer Staples | 101 | 38 | 40 | 17 | 5 | 5.9% | 4.9% |
| Materials | 94 | 34 | 35 | 24 | 2 | 5.6% | 5.1% |
| Real Estate | 84 | 10 | 40 | 32 | 2 | 5.7% | 6.9% |
| Communication Services | 80 | 31 | 28 | 13 | 5 | 3.9% | 3.3% |
| Utilities | 60 | 13 | 35 | 12 | 0 | 4% | 4% |
| All sectors | 1,763 | 422 | 740 | 514 | 84 | 100% | 100% |
Sample: n = 1,763 of the 1,767 companies. Size by latest market value for the 1,338 active companies with one: large ≥ $10bn, mid $2–10bn, small < $2bn. S&P 1500 shares count the constituents of the S&P 500, MidCap 400 and SmallCap 600 (1,506 companies, lists read Sep 25, 2026). Sectors are each company's current GICS sector.
2.2Signals
| Signal | Definition | Since | Wednesdays |
|---|---|---|---|
| Recent 13D stake | At least one Schedule 13D (a stake above 5% with intent to influence) filed in the previous 90 days and already public | Jan 4, 1995 | 1,633 |
| Activist share of large holders | Of the stock's holders above 5% on file, the share that filed an activist 13D rather than a passive 13G | Jan 17, 2001 | 1,321 |
2.3Measurement
Outcome. The return from the close on the Wednesday to the close 1, 5, 21 and 63 trading sessions later, on closes adjusted for splits and dividends, compared with the same day's median stock; half of all stocks beat the median by construction, so chance is 50 in 100 on every date. No delisting return is added.
Each Wednesday, the stocks showing the reading are scored against the same day's median stock. A state counts on every Wednesday it holds; a cross or breakout counts only on the Wednesday it happens.
Each Wednesday the stocks are ranked on the signal. The study reports how often each fifth of that ranking beat the median stock, and the rank correlation (IC) between the signal and the return that followed.
The t-statistic uses non-overlapping dates only. A result is called proven when |t| is at least 3, it held in at least 60% of years and it is large enough to matter; with 1,470 tests across the studies, a looser bar would pass dozens by luck.
Full data and methods3Results
Figure 1 reads every horizon. Stocks with a 13D filed in the previous 90 days beat the median stock 49 times in 100 over the next session, 49 over the next week, 49 over the next month and 50 over the next three months. The two shortest readings lean a little below a coin flip, faint rather than proven; the month and the quarter show no measurable edge. None of the four is a relation in the belief's direction.
Share of stocks showing the reading that beat the same day's median stock, by horizon. The line at 50 is chance, the grey band the range chance alone produces; a filled square is a proven relation.
Rank correlation between the signal and the return that followed, with its 95% interval. An interval that crosses zero is no relation.
Each square is one calendar year; filled = a year in which the average stock showing the signal lagged the median stock over the next month. Years are counted, not shown in order.
A signal with an edge would fill most squares, or leave most empty.
Rank correlation inside each GICS sector over the next month, stocks ranked only against their own sector. Colour only where |t| ≥ 2.
Out of every 100 stocks carrying a recent 13D stake, 49 beat the median stock over the following month (Figure 2). Ranked instead by the share of a stock's large holders that are activists, the rank correlation with the next month's return was -0.007 (Figure 3): close to zero, and slightly negative rather than positive.
Studies of activism find that prices react in the days around the filing itself (Brav, Jiang, Partnoy and Thomas 2008). One likely reason: by the time the stake is public and counted here, the news is in the price, and what followed was, on average, an ordinary month against the median stock.
4Robustness
Table 3 reads the 13D flag horizon by horizon: over the next month it lagged the median stock in 22 of 32 years and beat it in the rest. In Table 4 the activist-share ranking kept a slightly negative sign in every period Table 4 shows, in 7 of 11 sectors and among S&P 500 members on the date (IC -0.011, t -2.7), but nowhere strongly enough to count as a proven relation; if anything, it leaned slightly against the belief.
Share that beat the median stock, its t-statistic on non-overlapping dates, and the years in which it pointed the same way.
| Horizon | Beat the median | t | Years, same way |
|---|---|---|---|
| Recent 13D stake, session | 49.1 | -5.4 | 26 / 32 |
| Recent 13D stake, week | 49.5 | -3.3 | 23 / 32 |
| Recent 13D stake, month | 49.4 | -1.7 | 22 / 32 |
| Recent 13D stake, three months | 49.5 | -0.2 | 21 / 32 |
Rank IC and its t-statistic on non-overlapping dates.
| Sample | IC | t | Wednesdays |
|---|---|---|---|
| Activist share of large holders, next month | |||
| All stocks, whole period | -0.0067 | -2.0 | 1,316 |
| By decade: 1995–2004 | -0.0041 | -0.6 | 202 |
| By decade: 2005–2014 | -0.0037 | -0.8 | 518 |
| By decade: 2015– | -0.0102 | -2.0 | 596 |
| S&P 500 members on the date | -0.0107 | -2.7 | 1,312 |
| Sectors with the overall sign | 7 / 11 |
5Limitations
- The flag counts a stake only once its filing is public, so the move on the filing day itself is not in the sample: the study measures what came after the announcement, not the announcement. A stake also counts on every Wednesday of its 90 days, so one campaign is scored several times.
- The activist-share ranking covers only stocks with at least one large holder on file, and its record starts later than the 13D flag's; Table 2 gives both start dates.
- Before costs. Averages exclude trading costs, taxes and market impact.
- Same-close timing. Returns start at the close the signal is computed from; a real trade would start later.
- Survivors among smaller companies. The non-index names were chosen from companies listed when the universe was built; no delisting returns are added.
6Conclusion
A 13D filing says that an investor holds a large stake and intends to push for change. It is news about a company's owners, and studies find the price reacts when it appears. Measured from the moment the filing was public, against the same day's median stock, stocks with a recent activist stake did not go on to beat other stocks by a measurable margin, and a larger activist presence among the holders did not help. The filing describes who owns the company, not where its price goes next.
References
- Brav, A., Jiang, W., Partnoy, F. and Thomas, R. (2008). Hedge Fund Activism, Corporate Governance, and Firm Performance. Journal of Finance 63(4).
- Bebchuk, L. A., Brav, A. and Jiang, W. (2015). The Long-Term Effects of Hedge Fund Activism. Columbia Law Review 115(5).
- Benjamini, Y. and Hochberg, Y. (1995). Controlling the False Discovery Rate: A Practical and Powerful Approach to Multiple Testing. Journal of the Royal Statistical Society, Series B 57(1).
- Grinold, R. C. and Kahn, R. N. (2000). Active Portfolio Management, 2nd ed. McGraw-Hill.
- Harvey, C. R., Liu, Y. and Zhu, H. (2016). … and the Cross-Section of Expected Returns. Review of Financial Studies 29(1).
- Shumway, T. (1997). The Delisting Bias in CRSP Data. Journal of Finance 52(1).
Appendix A. Questions readers ask
- Do stocks go up after an activist investor takes a stake?
- Not by more than other stocks, once the filing is public. Studies find that the price reacts around the filing itself; after that, since 1995, US stocks with a 13D stake filed in the previous 90 days beat the same day's median stock over the next month 49 times in 100, and over three months 50 times, against 50 for a coin flip.
- What is a 13D filing?
- An investor who acquires more than five percent of a US company's shares with the intent to influence how it is run must file a Schedule 13D with the SEC within days. Investors without that intent file the shorter 13G. A 13D is the public mark of an activist stake.
- Why don't the stocks go on to beat other stocks?
- Studies of activism find that prices react in the days around the filing itself (Brav, Jiang, Partnoy and Thomas 2008). One likely reason: by the time the stake is public and counted here, the news is in the price, and what followed was, on average, an ordinary month against the median stock.
- How were activist stakes measured?
- Every Wednesday from Jan 4, 1995 to Aug 19, 2026, the stocks with a 13D filed in the previous 90 days, counted only once the filing was public, were compared with the same day's median stock over the next 1, 5, 21 and 63 trading sessions, on the same universe of 1,767 US stocks every study uses.
Data availability and citation
Every figure in this paper is quoted from one frozen snapshot, published as JSON with the sample description, the robustness results and the test counts. The same snapshot feeds the research console, so the two cannot disagree.
Opulence Alpha Research (2026). Do stocks beat the rest once an activist investor's 13D is public? Opulence Alpha Studies, Sep 25, 2026. https://opulencealpha.ai/studies/activist-stakes
Research, not advice. A measured tendency across hundreds of stocks is a nudge for any one of them, never a forecast of its price.