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Index change event
S&P index changes, effective 18 and 20 August 2026
Reddit joined the S&P 500 and AvalonBay Communities left it. Two days later the MidCap 400 changed as well.
Announced
2026-08-13
Effective
August 17, 2026 at 5:00:00 PM
Indexes Affected
2
What happened to the prices
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Reddit is the only addition to the S&P 500.
The two effective dates are two days apart.
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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
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Reddit | RDDT | S&P 500 | 08/18/2026 |
S&P MidCap 400
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Sun Communities | SUI | S&P MidCap 400 | 08/20/2026 |
S&P SmallCap 600
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
S&P 100
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.
Additions
Company | Ticker | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|
Reddit | RDDT | 158.12 | +16.55% | ||||
Sun Communities | SUI | 120.19 | +4.46% |
Deletions
Company | Ticker | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|
AvalonBay Communities | AVB | ||||||
Webster Financial | WBS |
Not a Investment Advice
This page is research about past price behaviour. It is not a recommendation to buy or sell.
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