Index change event
S&P 500, MidCap 400 & SmallCap 600 Additions & Index Changes: APP, EME, HOOD, KTOS, MP, NTNX, TRU, ACHC, CZR, ENPH, HL, MAN, MKTX, NE, QTWO, WEN & WAY – 5th September 2025
On 5 September 2025, S&P Dow Jones Indices announced 36 index changes affecting 27 companies in the S&P 100, S&P 500, S&P MidCap 400 and S&P SmallCap 600. The most notable move was AppLovin joining the S&P 500.
Announced
2025-09-05
Effective
September 21, 2025 at 5:00:00 PM
Indexes Affected
S&P 100, S&P 500, S&P MidCap 400, S&P SmallCap 600
36
Index Changes in Total
18
Additions
18
Deletions
9
Companies that changed index
What happened to the prices
By the next day's close, the 12 additions with price data had peaked at an average of +6.95%, against +2.25% for the 15 deletions. The largest mover was Robinhood Markets, with a peak of +15.74%. 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.
Charter Communications went against the other deletions: its next-day open was -2.32% from the post-announcement price, while the 15 deletions averaged +0.23%.
In Short
36 index changes: 18 additions and 18 deletions.
9 companies moved from one S&P index to another, out of 27 in total.
Largest peak move: Robinhood Markets, +15.74% 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: AppLovin (APP), Emcor Group (EME) and Robinhood Markets (HOOD)
3 companies joined the S&P 500 and 3 left, effective 22 September 2025. Emcor Group moved up from the S&P MidCap 400; AppLovin and Robinhood Markets are new to the S&P family; Caesars Entertainment, Enphase Energy and MarketAxess Holdings moved down to the S&P SmallCap 600. The 3 additions with price data peaked at an average of +9.67% by the next day's close, led by Robinhood Markets at +15.74%.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
AppLovin | APP | S&P 500 | 09/22/2025 | |
Emcor Group | EME | S&P MidCap 400 | S&P 500 | 09/22/2025 |
Robinhood Markets | HOOD | S&P 500 | 09/22/2025 |
S&P MidCap 400 Additions: Kratos Defense & Security Solutions (KTOS), MP Materials (MP), Nutanix (NTNX) and 1 more
4 companies joined the S&P MidCap 400 and 4 left, effective 22 September 2025. Kratos Defense & Security Solutions and MP Materials moved up from the S&P SmallCap 600; Nutanix and TransUnion are new to the S&P family; Emcor Group moved up to the S&P 500; Acadia Healthcare Company, ManpowerGroup and The Wendy's Company moved down to the S&P SmallCap 600. The 4 additions with price data peaked at an average of +3.75% by the next day's close, led by Nutanix at +8.53%.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Kratos Defense & Security Solutions | KTOS | S&P SmallCap 600 | S&P MidCap 400 | 09/22/2025 |
MP Materials | MP | S&P SmallCap 600 | S&P MidCap 400 | 09/22/2025 |
Nutanix | NTNX | S&P MidCap 400 | 09/22/2025 | |
TransUnion | TRU | S&P MidCap 400 | 09/22/2025 |
S&P SmallCap 600 Additions: Caesars Entertainment (CZR), Enphase Energy (ENPH), MarketAxess Holdings (MKTX) and 7 more
10 companies joined the S&P SmallCap 600 and 10 left, effective 22 September 2025. Of the 10 additions, 3 moved down from the S&P 500, 3 moved down from the S&P MidCap 400 and 4 are new to the S&P family; of the 10 deletions, 2 moved up to the S&P MidCap 400 and 8 left the S&P family. The 10 additions with price data peaked at an average of +4.43% by the next day's close, led by Hecla Mining at +13.97%.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Acadia Healthcare Company | ACHC | S&P MidCap 400 | S&P SmallCap 600 | 09/22/2025 |
Caesars Entertainment | CZR | S&P 500 | S&P SmallCap 600 | 09/22/2025 |
Enphase Energy | ENPH | S&P 500 | S&P SmallCap 600 | 09/22/2025 |
Hecla Mining | HL | S&P SmallCap 600 | 09/22/2025 | |
ManpowerGroup | MAN | S&P MidCap 400 | S&P SmallCap 600 | 09/22/2025 |
MarketAxess Holdings | MKTX | S&P 500 | S&P SmallCap 600 | 09/22/2025 |
Noble Corporation | NE | S&P SmallCap 600 | 09/22/2025 | |
Q2 Holdings | QTWO | S&P SmallCap 600 | 09/22/2025 | |
The Wendy's Company | WEN | S&P MidCap 400 | S&P SmallCap 600 | 09/22/2025 |
Waystar Holding | WAY | S&P SmallCap 600 | 09/22/2025 |
S&P 100 Additions: Uber Technologies (UBER)
1 company joined the S&P 100 and 1 left, effective 22 September 2025. Uber Technologies joined and Charter Communications left the S&P 100. Uber Technologies peaked at +4.20% by the next day's close.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Uber Technologies | UBER | S&P 100 | 09/22/2025 |
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 |
|---|---|---|---|---|---|---|---|---|---|---|
AppLovin | APP | S&P 500 | 490.24 | 493.16 | +7.29% | +6.78% | +5.84% | +8.90% | +12.64% | |
Emcor Group | EME | S&P MidCap 400 | S&P 500 | 625.40 | 643.99 | 0.00% | -0.31% | -0.81% | -2.09% | +0.62% |
Robinhood Markets | HOOD | S&P 500 | 101.25 | 101.35 | +7.44% | +7.19% | +5.90% | +9.16% | +15.74% |
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 |
|---|---|---|---|---|---|---|---|---|---|---|
Kratos Defense & Security Solutions | KTOS | S&P SmallCap 600 | S&P MidCap 400 | 64.81 | 64.81 | 0.00% | -1.20% | -0.12% | +0.05% | +1.22% |
MP Materials | MP | S&P SmallCap 600 | S&P MidCap 400 | 63.05 | 62.94 | 0.00% | -0.81% | -0.14% | -0.46% | +0.91% |
Nutanix | NTNX | S&P MidCap 400 | 69.92 | 70.10 | +3.24% | +2.92% | +2.72% | +3.12% | +8.53% | |
TransUnion | TRU | S&P MidCap 400 | 90.02 | 91.34 | +1.86% | +1.83% | +1.86% | +2.50% | +4.34% |
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 |
|---|---|---|---|---|---|---|---|---|---|---|
Acadia Healthcare Company | ACHC | S&P MidCap 400 | S&P SmallCap 600 | 23.72 | 24.21 | 0.00% | -1.34% | +0.28% | -0.93% | +0.60% |
Caesars Entertainment | CZR | S&P 500 | S&P SmallCap 600 | 26.34 | 25.98 | 0.00% | +0.42% | +1.00% | +1.46% | +2.39% |
Enphase Energy | ENPH | S&P 500 | S&P SmallCap 600 | 39.65 | 39.66 | -0.40% | -2.07% | -2.24% | -0.20% | 0.00% |
Hecla Mining | HL | S&P SmallCap 600 | 9.02 | 9.02 | +1.44% | +3.10% | +2.33% | +4.71% | +13.97% | |
ManpowerGroup | MAN | S&P MidCap 400 | S&P SmallCap 600 | 41.26 | 41.26 | 0.00% | +0.70% | +0.70% | -0.39% | +2.71% |
MarketAxess Holdings | MKTX | S&P 500 | S&P SmallCap 600 | 187.50 | 184.53 | 0.00% | 0.00% | +2.41% | +1.89% | +2.58% |
Noble Corporation | NE | S&P SmallCap 600 | 28.60 | 28.65 | +3.11% | +3.07% | +4.05% | +5.20% | +7.33% | |
Q2 Holdings | QTWO | S&P SmallCap 600 | 78.81 | 80.01 | +1.51% | +1.51% | +0.61% | +2.07% | +6.19% | |
The Wendy's Company | WEN | S&P MidCap 400 | S&P SmallCap 600 | 10.33 | 10.31 | +0.19% | +0.19% | 0.00% | -0.10% | +0.77% |
Waystar Holding | WAY | S&P SmallCap 600 | 37.27 | 37.96 | +0.21% | +0.63% | +1.42% | +1.24% | +7.72% |
Not a Investment Advice
This page is research about past price behaviour. It is not a recommendation to buy or sell.