What Happened?
Shares of online community and discussion platform Reddit (NYSE: RDDT) jumped 13.8% in the morning session after S&P Dow Jones Indices announced the social media company will join the S&P 500, replacing AvalonBay Communities (NYSE: AVB), effective prior to the open on Tuesday, August 18. The stock jumped in Thursday’s extended session and held the move into Friday’s regular trading. S&P 500 trackers must own every constituent, so Reddit gets a large, mechanical bid into a name that had already been sold down on growth and traffic worries.
The vacancy is merger-driven, not a rotation out of real estate. Equity Residential is acquiring AvalonBay; the combined company—to be renamed Vivmark Residential—stays in the S&P 500, and Reddit fills the open Communication Services slot.
That puts Reddit beside Meta as only the second pure-play social media stock in the benchmark.
According to Reuters, J.P. Morgan estimated passive funds may need to buy roughly 16.7 million shares—nearly three times Reddit’s average daily volume of about 5.98 million shares since its March 2024 IPO, per LSEG data—enough to move a mid-cap with thin float relative to index AUM. The tape context amplifies the reaction: through Thursday’s close, RDDT was down more than 31% year to date and more than 42% from its September 2025 high after a late-July quarter where sales growth still topped 60% but management flagged “choppy” search referrals as Google pushed Gemini-powered AI Overviews. Inclusion does not resolve that user-acquisition risk. Historically, new S&P additions often run from announcement to the effective date and then underperform over the following months once index buying is complete—so the next checkpoint is whether the August 18 rebalance absorbs supply without a fade.
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What Is The Market Telling Us
Reddit’s shares are extremely volatile and have had 53 moves greater than 5% over the last year. But moves this big are rare even for Reddit and indicate this news significantly impacted the market’s perception of the business.
The previous big move we wrote about was 7 days ago when the stock gained 6.4% on the news that the July jobs report showed an unexpected loss of 23,000 jobs, signaling a cooling labor market. Economists had forecast a gain of around 80,000 nonfarm payrolls. According to the U.S. Bureau of Labor Statistics, the unemployment rate held steady at 4.1%. This weaker-than-expected data led investors to bet on the possibility of an interest rate cut by the Federal Reserve.
The logic, often described as "bad news is good news" for the market, suggests that a slowing economy could deter the central bank from further rate hikes, and potentially encourage cuts to stimulate growth. This outlook generally makes borrowing cheaper for companies and increases the relative attractiveness of stocks.
Reddit is down 26.3% since the beginning of the year, and at $178.26 per share, it is trading 34.2% below its 52-week high of $270.71 from September 2025. Investors who bought $1,000 worth of Reddit’s shares at the IPO in March 2024 would now be looking at an investment worth $3,534.
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