Index change event
S&P MidCap 400 Additions & Index Changes: SIRI – 8th June 2026
On 8 June 2026, S&P Dow Jones Indices announced 2 index changes affecting 2 companies in the S&P MidCap 400. Sirius XM Holdings replaced Masimo in the S&P MidCap 400.
Announced
2026-06-08
Effective
June 10, 2026 at 5:00:00 PM
Indexes Affected
S&P MidCap 400
2
Index Changes in Total
1
Additions
1
Deletions
0
Companies that changed index
What happened to the prices
By the next day's close, Sirius XM Holdings, the only addition with price data, had peaked at +5.53%, against +0.03% for Masimo, the only deletion with price data. The moves are measured from the first extended-hours price after the 17:15 ET announcement.
With one addition and one deletion priced, there is no group to stand out from: Sirius XM Holdings opened the next day at +4.26% and Masimo at +0.01%, both from the first price after the announcement.
In Short
2 index changes: 1 addition and 1 deletion.
No company moved from one S&P index to another in this announcement.
Largest peak move: Sirius XM Holdings, +5.53% 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.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
S&P MidCap 400 Additions: Sirius XM Holdings (SIRI)
1 company joined the S&P MidCap 400 and 1 left, effective 11 June 2026. Sirius XM Holdings is new to the S&P family and Masimo left the S&P family. Sirius XM Holdings peaked at +5.53% by the next day's close.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Sirius XM Holdings | SIRI | S&P MidCap 400 | 06/11/2026 |
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Price reaction
The close price is the last price before the announcement. All percentages are measured from the open price after the announcement.
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 |
|---|---|---|---|---|---|---|---|---|---|---|
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 |
|---|---|---|---|---|---|---|---|---|---|---|
Sirius XM Holdings | SIRI | S&P MidCap 400 | 27.44 | 27.48 | +4.62% | +4.11% | +3.55% | +4.26% | +5.53% |
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 |
|---|---|---|---|---|---|---|---|---|---|---|
Not a Investment Advice
This page is research about past price behaviour. It is not a recommendation to buy or sell.