Index change event
S&P 500, MidCap 400 & SmallCap 600 Additions & Index Changes: IBKR, TLN & KNTK – 25th August 2025
On 25 August 2025, S&P Dow Jones Indices announced 6 index changes affecting 5 companies in the S&P 500, S&P MidCap 400 and S&P SmallCap 600. The most notable move was Interactive Brokers Group joining the S&P 500 from the S&P MidCap 400.
Announced
2025-08-25
Effective
August 27, 2025 at 5:00:00 PM
Indexes Affected
S&P 500, S&P MidCap 400, S&P SmallCap 600
6
Index Changes in Total
3
Additions
3
Deletions
1
Companies that changed index
What happened to the prices
By the next day's close, the 3 additions with price data had peaked at an average of +5.94%, against +0.70% for the 2 deletions. The largest mover was Interactive Brokers Group, with a peak of +7.57%. The moves are measured from the first extended-hours price after the announcement, except for 1 name with no recorded trade after 17:15 ET, measured from the 16:00 ET close.
No name moved against its group: every addition with price data opened the next day above the post-announcement price and every deletion with price data opened below it.
In Short
6 index changes: 3 additions and 3 deletions.
1 company moved from one S&P index to another, out of 5 in total.
Largest peak move: Interactive Brokers Group, +7.57% by the next day's close.
The changes, index by index
An empty cell means the company was not in the S&P family before, or left it.
S&P 500 Additions: Interactive Brokers Group (IBKR)
1 company joined the S&P 500 and 1 left, effective 28 August 2025. Interactive Brokers Group moved up from the S&P MidCap 400 and Walgreens Boots Alliance left the S&P family. Interactive Brokers Group peaked at +7.57% by the next day's close.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Interactive Brokers Group | IBKR | S&P MidCap 400 | S&P 500 | 08/28/2025 |
S&P MidCap 400 Additions: Talen Energy (TLN)
1 company joined the S&P MidCap 400 and 1 left, effective 28 August 2025. Talen Energy is new to the S&P family and Interactive Brokers Group moved up to the S&P 500. Talen Energy peaked at +5.67% by the next day's close.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Talen Energy | TLN | S&P MidCap 400 | 08/28/2025 |
S&P SmallCap 600 Additions: Kinetik Holdings (KNTK)
1 company joined the S&P SmallCap 600 and 1 left, effective 2 September 2025. Kinetik Holdings is new to the S&P family and Pacific Premier Bancorp left the S&P family. Kinetik Holdings peaked at +4.58% by the next day's close.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Kinetik Holdings | KNTK | S&P SmallCap 600 | 09/02/2025 |
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Price reaction
The close price is the last price before the announcement. Percentages are measured from the open price after the announcement, or from the close for a company with no price after it.
S&P 500 Additions Changes
Company | Ticker | Source Index | Final Index | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Change by Next Day Open | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|---|---|---|
Interactive Brokers Group | IBKR | S&P MidCap 400 | S&P 500 | 62.76 | 62.98 | +3.21% | +4.00% | +3.54% | +2.41% | +7.57% |
S&P MidCap 400 Additions Changes
Company | Ticker | Source Index | Final Index | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Change by Next Day Open | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|---|---|---|
Talen Energy | TLN | S&P MidCap 400 | 355.53 | 359.75 | +2.32% | +2.32% | +2.97% | +4.21% | +5.67% |
S&P SmallCap 600 Additions Changes
Not a Investment Advice
Company | Ticker | Source Index | Final Index | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Change by Next Day Open | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|---|---|---|
Kinetik Holdings | KNTK | S&P SmallCap 600 | 40.64 | 41.46 | +4.58% | +4.44% | +4.58% | +2.12% | +4.58% |
Not a Investment Advice
This page is research about past price behaviour. It is not a recommendation to buy or sell.