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What will be the percentage change in the S&P 500 from close of Aug 26, 2026 to open of Aug 31, 2026?
0.135
Submitted p50
weighted_average
Fermi logic
unknown
Domain
Plan 42.15s
Sub-questions (0)
Research 0.74s, 0 tool(s), 0 error(s)
Cross-market signals
## Cross-Market Signals ### Polymarket - "Will there be no change in Fed interest rates after the September 2026 meeting?" → Yes: 0.71, Volume: $7.1M - "Will Shakhtar Donetsk win the 2026-27 UEFA Champions League Championship?" → Yes: 0.00, Volume: $4.5M - "Will the Fed increase interest rates by 25 bps after the September 2026 meeting?" → Yes: 0.28, Volume: $6.7M - "Will the Fed decrease interest rates by 25 bps after the September 2026 meeting?" → Yes: 0.01, Volume: $8.1M - "Will the Fed increase interest rates by 50+ bps after the September 2026 meeting?" → Yes: 0.00, Volume: $4.8M - "US announces end of Iranian blockade by August 15, 2026?" → Yes: 0.04, Volume: $2.7M - "Will Elon Musk post 120-139 tweets from August 7 to August 14, 2026?" → Yes: 0.00, Volume: $341.4K - "Will Elon Musk post 140-159 tweets from August 7 to August 14, 2026?" → Yes: 0.27, Volume: $213.5K - "US announces end of Iranian blockade by August 14, 2026?" → Yes: 0.02, Volume: $417.1K - "Will Elon Musk post 240-259 tweets from August 7 to August 14, 2026?" → Yes: 0.00, Volume: $177.2K
Evidence Synthesis 22.64s, 9 items
Since 1978 the S&P 500 has averaged +0.5% in the month following the first day of the Jackson Hole symposium.
The resolution window (Aug 26 close to Aug 31 open) spans roughly two trading sessions plus a weekend gap, i.e. ~3 calendar days.
Unconditional S&P 500 daily standard deviation is roughly 1%; over ~2.5 sessions this implies a distribution centered near 0% with ~1.3-1.6% dispersion.
Equity index returns have a small positive drift, making slightly-positive outcomes marginally more likely than negative over short horizons.
On Aug 22, 2025, the S&P 500 rose sharply (~+1.5%) after Powell's Jackson Hole speech signaled possible rate cuts.
The 2026 symposium topic is 'Financial Innovation: Implications for Payments and Policy,' not directly a monetary-policy-stance theme.
Chair Powell's term as Fed Chair expires May 2026, so the 2026 keynote may be delivered by a new or transitioning Chair, adding uncertainty to the policy signal.
Late August is typically a low-volume, low-realized-volatility period for US equities, which tends to compress short-horizon moves.
Using an open price as the endpoint adds an overnight/weekend gap component, which historically has slightly higher variance than intraday-to-intraday comparisons.
Information gaps
- No research data supplied at all — no news, prices, or market quotes
- Missing base rate: historical distribution of S&P 500 close-before-symposium to open-after-symposium changes
- No current VIX level, options-implied move, or recent realized volatility
- No 2026 macro context (inflation, Fed path, Chair identity, index level)
Key uncertainties
- Whether the keynote delivers a policy surprise (hawkish/dovish)
- Macro data releases falling within Aug 27-28, 2026
- Prevailing volatility regime in Aug 2026
- Non-Fed exogenous shocks over the weekend gap
Forecast 32.74s, opus, secondary
Rationale
(a) The question resolves Aug 31, 2026, and the measurement window itself is only ~3 calendar days (Aug 26 close → Aug 27 and Aug 28 sessions → Aug 31 open), i.e. about 2 trading days plus a weekend gap. (b) Status quo (no news, flat market) gives ~0%, so the distribution must be centered essentially at zero with a tiny positive drift. (c) A continuing bull-drift trend would imply roughly +0.1% to +0.3% over 2.5 sessions, which is well within noise. (d) Base rates: unconditional S&P daily sigma ~0.9-1.1%, so ~2.5-3 units of variance implies sigma ~1.3-1.6%; late-August low-liquidity regimes typically compress this toward ~1.0-1.3%. Jackson Hole historically adds mild event risk, but the 2026 theme is payments/financial innovation rather than the policy stance, and Polymarket's September FOMC pricing (71% hold, 28% hike) suggests policy expectations are fairly settled though with hawkish tail risk — that hike-risk pricing argues for slightly fatter downside than a pure random walk. (e) LOW scenario (~p10): a hawkish keynote from a transitioning Fed leadership, hot inflation/PCE data on Aug 28, or a weekend geopolitical/credit shock gapping Monday's open down 1.5-2%. (f) HIGH scenario (~p90): a dovish or reassuring keynote plus soft inflation data producing a 1.5-2% two-day melt-up, echoing the ~+1.5% single-day move after Powell's 2025 speech. I center at +0.1%, use an effective sigma near 1.2%, and widen the tails modestly for unknown unknowns and the possibility of an elevated-volatility regime, acknowledging the hard -2% floor truncates the left tail.
Evidence brief shown to forecaster
1. [sq1 | question_description | MODERATE cred 60 | NEUTRAL | DATED] Since 1978 the S&P 500 has averaged +0.5% in the month following the first day of the Jackson Hole symposium. 2. [sq1 | question_description | STRONG cred 95 | NEUTRAL | VERY_RECENT] The resolution window (Aug 26 close to Aug 31 open) spans roughly two trading sessions plus a weekend gap, i.e. ~3 calendar days. 3. [sq1 | general_market_knowledge | MODERATE cred 70 | NEUTRAL | DATED] Unconditional S&P 500 daily standard deviation is roughly 1%; over ~2.5 sessions this implies a distribution centered near 0% with ~1.3-1.6% dispersion. 4. [sq1 | general_market_knowledge | WEAK cred 65 | UP | DATED] Equity index returns have a small positive drift, making slightly-positive outcomes marginally more likely than negative over short horizons. 5. [sq1 | question_description | MODERATE cred 80 | NEUTRAL | DATED] On Aug 22, 2025, the S&P 500 rose sharply (~+1.5%) after Powell's Jackson Hole speech signaled possible rate cuts. 6. [sq1 | question_description | MODERATE cred 90 | NEUTRAL | VERY_RECENT] The 2026 symposium topic is 'Financial Innovation: Implications for Payments and Policy,' not directly a monetary-policy-stance theme. 7. [sq1 | general_market_knowledge | WEAK cred 60 | NEUTRAL | DATED] Chair Powell's term as Fed Chair expires May 2026, so the 2026 keynote may be delivered by a new or transitioning Chair, adding uncertainty to the policy signal. 8. [sq1 | general_market_knowledge | WEAK cred 60 | NEUTRAL | DATED] Late August is typically a low-volume, low-realized-volatility period for US equities, which tends to compress short-horizon moves. 9. [sq1 | resolution_criteria | WEAK cred 55 | NEUTRAL | DATED] Using an open price as the endpoint adds an overnight/weekend gap component, which historically has slightly higher variance than intraday-to-intraday comparisons. ## Cross-Market Signals ### Polymarket - "Will there be no change in Fed interest rates after the September 2026 meeting?" → Yes: 0.71, Volume: $7.1M - "Will Shakhtar Donetsk win the 2026-27 UEFA Champions League Championship?" → Yes: 0.00, Volume: $4.5M - "Will the Fed increase interest rates by 25 bps after the September 2026 meeting?" → Yes: 0.28, Volume: $6.7M - "Will the Fed decrease interest rates by 25 bps after the September 2026 meeting?" → Yes: 0.01, Volume: $8.1M - "Will the Fed increase interest rates by 50+ bps after the September 2026 meeting?" → Yes: 0.00, Volume: $4.8M - "US announces end of Iranian blockade by August 15, 2026?" → Yes: 0.04, Volume: $2.7M - "Will Elon Musk post 120-139 tweets from August 7 to August 14, 2026?" → Yes: 0.00, Volume: $341.4K - "Will Elon Musk post 140-159 tweets from August 7 to August 14, 2026?" → Yes: 0.27, Volume: $213.5K - "US announces end of Iranian blockade by August 14, 2026?" → Yes: 0.02, Volume: $417.1K - "Will Elon Musk post 240-259 tweets from August 7 to August 14, 2026?" → Yes: 0.00, Volume: $177.2K Information gaps: - No research data supplied at all — no news, prices, or market quotes - Missing base rate: historical distribution of S&P 500 close-before-symposium to open-after-symposium changes - No current VIX level, options-implied move, or recent realized volatility - No 2026 macro context (inflation, Fed path, Chair identity, index level) Key uncertainties: - Whether the keynote delivers a policy surprise (hawkish/dovish) - Macro data releases falling within Aug 27-28, 2026 - Prevailing volatility regime in Aug 2026 - Non-Fed exogenous shocks over the weekend gap
Raw forecast prompt
You are an elite superforecaster. Produce a probability distribution over the answer to this Metaculus numeric question.
## Question
What will be the percentage change in the S&P 500 from close of Aug 26, 2026 to open of Aug 31, 2026?
## Description / Resolution Criteria
## Description
The [Jackson Hole Economic Policy Symposium](https://www.kansascityfed.org/research/jackson-hole-economic-symposium/about-jackson-hole-economic-symposium/) is an annual event hosted by the Federal Reserve Bank of Kansas City in Jackson Hole, Wyoming. It brings together central bankers, policymakers, academics, and economists from around the world and is one of the longest-standing central banking conferences in the world. Given the participants and the topics being discussed, there is substantial interest in the symposium. In particular, investors are given some clarity about the Federal Reserve System's plans for monetary policy. This in turn can reduce volatility in the markets.
[Some data analysis](https://ceooutlookmagazine.com/news/what-can-we-learn-from-historical-stock-market-performance-after-jackson-hole/) shows
> the Dow Jones Industrial Average has gained an average of 0.3% in the month following the first day of the Jackson Hole meeting since 1978. The S\&P 500 has risen an average of 0.5%, and the Nasdaq Composite has climbed an average of 0.9%.
For example, [the US stock market surged](https://markethighlow.com/us-stock-market-jumps-as-powell-signals-possible-rate-cuts-at-jackson-hole-august-22-2025/) on August 22, 2025, after Federal Reserve Chair Jerome Powell delivered a speech hinting at interest rate cuts at the symposium.
The 2026 Symposium will take place August 27-29 with the topic of "Financial Innovation: Implications for Payments and Policy."
`{"format": "metac_reveal_and_close_in_period", "info": {"post_id": 44532, "question_id": 44678}}`
## Resolution Criteria
This question will resolve as the percentage change from the non-adjusted closing price of the S\&P 500 Index (^GSPC) according to [Yahoo! Finance](https://uk.finance.yahoo.com/quote/%5EGSPC/history/) on August 26, 2026, to the open price of the S\&P 500 on August 31, 2026. These prices are the last before the symposium and the first afterwards.
For example, if the dates were June 3 (\$7,553.68 close) and June 8 (\$7,440.57 open) the resolution would be -1.49742%.
## Fine Print
This question's information (resolution criteria, fine print, background info, etc) is synced with an [original identical question](https://www.metaculus.com/questions/44532) which opened on 2026-08-10 17:00:00. This question will resolve based on the resolution criteria and fine print of the linked original question. However, if this question would resolve differently than the original question, then this question will be annulled. Additionally, if the original question's resolution could have been known before this question opened, then this question will be annulled.
## Range
The answer must be a number in [-2, 5] (units: %).
## Sub-question decomposition (planner)
(none)
## Synthesized evidence
1. [sq1 | question_description | MODERATE cred 60 | NEUTRAL | DATED] Since 1978 the S&P 500 has averaged +0.5% in the month following the first day of the Jackson Hole symposium.
2. [sq1 | question_description | STRONG cred 95 | NEUTRAL | VERY_RECENT] The resolution window (Aug 26 close to Aug 31 open) spans roughly two trading sessions plus a weekend gap, i.e. ~3 calendar days.
3. [sq1 | general_market_knowledge | MODERATE cred 70 | NEUTRAL | DATED] Unconditional S&P 500 daily standard deviation is roughly 1%; over ~2.5 sessions this implies a distribution centered near 0% with ~1.3-1.6% dispersion.
4. [sq1 | general_market_knowledge | WEAK cred 65 | UP | DATED] Equity index returns have a small positive drift, making slightly-positive outcomes marginally more likely than negative over short horizons.
5. [sq1 | question_description | MODERATE cred 80 | NEUTRAL | DATED] On Aug 22, 2025, the S&P 500 rose sharply (~+1.5%) after Powell's Jackson Hole speech signaled possible rate cuts.
6. [sq1 | question_description | MODERATE cred 90 | NEUTRAL | VERY_RECENT] The 2026 symposium topic is 'Financial Innovation: Implications for Payments and Policy,' not directly a monetary-policy-stance theme.
7. [sq1 | general_market_knowledge | WEAK cred 60 | NEUTRAL | DATED] Chair Powell's term as Fed Chair expires May 2026, so the 2026 keynote may be delivered by a new or transitioning Chair, adding uncertainty to the policy signal.
8. [sq1 | general_market_knowledge | WEAK cred 60 | NEUTRAL | DATED] Late August is typically a low-volume, low-realized-volatility period for US equities, which tends to compress short-horizon moves.
9. [sq1 | resolution_criteria | WEAK cred 55 | NEUTRAL | DATED] Using an open price as the endpoint adds an overnight/weekend gap component, which historically has slightly higher variance than intraday-to-intraday comparisons.
## Cross-Market Signals
### Polymarket
- "Will there be no change in Fed interest rates after the September 2026 meeting?" → Yes: 0.71, Volume: $7.1M
- "Will Shakhtar Donetsk win the 2026-27 UEFA Champions League Championship?" → Yes: 0.00, Volume: $4.5M
- "Will the Fed increase interest rates by 25 bps after the September 2026 meeting?" → Yes: 0.28, Volume: $6.7M
- "Will the Fed decrease interest rates by 25 bps after the September 2026 meeting?" → Yes: 0.01, Volume: $8.1M
- "Will the Fed increase interest rates by 50+ bps after the September 2026 meeting?" → Yes: 0.00, Volume: $4.8M
- "US announces end of Iranian blockade by August 15, 2026?" → Yes: 0.04, Volume: $2.7M
- "Will Elon Musk post 120-139 tweets from August 7 to August 14, 2026?" → Yes: 0.00, Volume: $341.4K
- "Will Elon Musk post 140-159 tweets from August 7 to August 14, 2026?" → Yes: 0.27, Volume: $213.5K
- "US announces end of Iranian blockade by August 14, 2026?" → Yes: 0.02, Volume: $417.1K
- "Will Elon Musk post 240-259 tweets from August 7 to August 14, 2026?" → Yes: 0.00, Volume: $177.2K
Information gaps:
- No research data supplied at all — no news, prices, or market quotes
- Missing base rate: historical distribution of S&P 500 close-before-symposium to open-after-symposium changes
- No current VIX level, options-implied move, or recent realized volatility
- No 2026 macro context (inflation, Fed path, Chair identity, index level)
Key uncertainties:
- Whether the keynote delivers a policy surprise (hawkish/dovish)
- Macro data releases falling within Aug 27-28, 2026
- Prevailing volatility regime in Aug 2026
- Non-Fed exogenous shocks over the weekend gap
## Required pre-forecast walkthrough
Before giving percentiles, address these explicitly in your rationale:
(a) The time left until the question resolves.
(b) The outcome if NOTHING changes from today (the status quo value).
(c) The outcome if the CURRENT TREND continues.
(d) The expectations of experts / markets / base rates.
(e) A plausible scenario that produces a LOW outcome (near p10).
(f) A plausible scenario that produces a HIGH outcome (near p90).
## Calibration guidance
- **Be humble about tails.** Good forecasters set WIDE 90/10 intervals to account for unknown unknowns. Narrow tails get punished by the log score far more than slightly-biased medians.
- **Status quo anchoring.** The p50 should be close to the status quo value unless you have strong evidence of a trend.
- Don't pile mass at one value — if you're tempted, widen the spread by 20-50%.
- **Anchor on markets/experts.** If liquid market prices, analyst forecasts, or community percentiles appear in the evidence, center your distribution on them and widen — don't override a liquid market without specific evidence it lacks.
- **Relative-return / spread questions ("how much will X's return exceed Y's").** A near-zero median is usually right, but size the TAILS to the more VOLATILE leg, not to a generic 2-3pp spread. Two broad equity indices (e.g. Nasdaq-100 vs S&P 500) do stay within roughly ±2-3pp over a two-week window. But when one leg is a commodity (crude oil, gold) or a single high-beta stock (e.g. Nvidia), the two-week realized spread regularly reaches ±10pp or more — crude-vs-equity spreads have hit ±18pp. In those cases set p10/p90 to at least ±10pp (±15pp or wider for oil) while keeping the median near the status-quo spread; the 2-3pp intuition applies only to index-vs-index.
- **Heavy-tailed one-off magnitudes (opening-weekend box office, product-launch or debut numbers).** Pre-event tracking for these routinely misses by ±40% or more, and results land both far above and far below the consensus. Do NOT treat the displayed [min, max] range as the plausible range or clamp p10/p90 to its edges: the outcome can fall outside the range in either direction (recent opening weekends resolved ~7% above a displayed ceiling in one case and roughly half the displayed floor in another). Set p10/p90 wide enough that a 2x-or-0.5x surprise versus your central estimate still lands inside the interval, and when concrete current tracking disagrees with historical/franchise base rates, weight the tracking.
## Output
Return ONLY valid JSON, no markdown fences:
{
"rationale": "<address (a) through (f) above, then state your distribution — 6-10 sentences total>",
"p10": <number>,
"p25": <number>,
"p50": <number>,
"p75": <number>,
"p90": <number>
}
Percentiles MUST be in non-decreasing order (p10 <= p25 <= p50 <= p75 <= p90).