• A stock split increases the number of shares and proportionally reduces the price per share, without changing the company’s total market value through the split itself.
  • Raw share volume can rise sharply after a split without a comparable increase in the dollar value of trading.
  • Evidence on post-split volatility is mixed, with results varying across companies, periods and the measures used.

A stock split divides each existing share into multiple new shares. The price per share drops in proportion, but the company’s total market value stays the same.

Nothing about the underlying business changes on the day of a split. What often does change, at least for a while, is how actively the stock trades.

It’s like cutting a pie into smaller pieces. You’ll end up with more slices, but the total amount remains the same.

The Volume Spike Is Mostly Arithmetic, Not New Buying

Cboe’s North American Execution Consulting Team published a study in May 2022 examining 61 stocks that had completed forward splits since 2020. Its mega-cap group contained only Apple, Tesla and Nvidia, so those findings reflect a small sample. ⁽¹⁾

Apple’s 2020 split offers one clear example. The 4-for-1 split took its share price from roughly $502 to $129.

Cboe reported that executed volume rose from roughly 47 million shares before the split to 225 million on the effective date. ⁽¹⁾ Dividing 225 million by four gives 56.25 million split-adjusted shares, approximately 20% above the earlier figure. Most of the apparent jump therefore reflects the larger share count, although adjusted activity also increased that day.

Across Cboe’s mega-cap sample, median split-adjusted volume was approximately 48% lower at the two-week to six-month post-split horizons than in the week before the split. ⁽¹⁾

Small Trades Can Add to Post-Split Volatility 

Cboe measured implied volatility, which reflects expectations of future price swings priced into options. In its mega-cap sample, this rose initially, fell back and increased again at six months; large-cap implied volatility remained elevated. ⁽¹⁾

Separately, Chen and Wu’s 2009 research linked higher return volatility after splits to increased small-trade activity. The researchers used small trades as a proxy for smaller investors, rather than directly identifying each trader as retail or institutional. ⁽²⁾

Nvidia said its June 2024 ten-for-one split was intended to make stock ownership more accessible to employees and investors. ⁽³⁾

However, higher volatility is not a universal outcome. Research published in 2026, covering 1962–2022, found that post-split increases in return volatility weakened after the 2001 reduction in minimum price increments. ⁽⁴⁾

In the same sample, raw volume increased only marginally in mid- and small-cap stocks, with some small-cap names recording declines. ⁽¹⁾

Higher Share Volume Does Not Guarantee Higher Dollar Turnover

A lower share price does not guarantee that a greater dollar amount will change hands. Trading turnover also cannot establish whether new investors entered the stock or whether capital flowed in.

Notional value traded, the total dollar amount changing hands, fell after most splits rather than rising. In Apple’s case, average daily notional value traded declined 9% after the 2020 split.

Average daily notional value traded in Apple options declined 47% after the split. ⁽¹⁾

Mid- and small-cap stocks saw investor exposure decline immediately after their splits, with no lasting pickup in the months that followed. ⁽¹⁾

Conclusion

A stock split changes the number of shares and the price per share. It does not, by itself, change what a company is worth or guarantee sustained new interest from investors. The data consistently shows:

  • Raw trading volume spikes immediately after a split, but split-adjusted volume is often flat or lower within weeks.
  • Volatility tends to rise for large and well-known stocks as smaller trades increase, then fades over time.
  • The effect concentrates in large-cap and mega-cap names, with limited impact on mid- and small-cap stocks.

For traders following large-cap names that dominate index performance, the short-term jump in activity around a split is a market structure event worth watching, distinct from any change in broader volatility conditions driven by wider economic or risk factors.

Sources: ⁽¹⁾ Cboe Global Markets, ⁽²⁾ International Review of Economics & Finance (Chen & Wu, 2009), ⁽³⁾ Nvidia Corporation, ⁽⁴⁾ Heavilin, J. E. & Songur, H. (2026), “Increases in volatility of returns after a stock split have mostly vanished: a reappraisal of Ohlson and Penman, 1985,” Critical Finance Review, 15(3), 388–418.