How might the timing of the presentation (4:00 pm ET) affect intraday liquidity and price volatility?

Short answer – Because the presentation is scheduled for 4:00 pm ET, i.e. exactly at the moment the U.S. equity markets close, the bulk of the price‑discovery process will happen in the after‑hours session (post‑close trading) and in the pre‑open of the next day. Liquidity at 4 pm is thin, spreads are wider and market‑maker participation is limited, so any new information that is released (or even the anticipation of it) can generate a disproportionately large price swing in the after‑hours market and can set the tone for the opening price on the following trading day.

Below is a step‑by‑step breakdown of the mechanisms that drive intraday liquidity and volatility when a company’s conference call or presentation is timed at the market close.

1. Market‑structure context for a 4 pm ET presentation

Because the presentation occurs at the exact close, the “real‑time” market cannot absorb the new information during the regular session. The reaction therefore shifts to the after‑hours market and to the next day’s opening auction.

2. How the 4 pm timing shapes intraday liquidity

Result: The price reaction to the presentation is compressed into a low‑liquidity environment, making each trade more “price‑effective”.

3. How the 4 pm timing fuels price volatility

1. Information‑release shock in a thin market

   • The presentation is likely to contain clinical‑trial updates, regulatory milestones, or financial guidance—information that historically moves CMPS shares.
     
   • In a thin after‑hours market, the first few trades that digest the news can create a large price swing (e.g., ±5‑10 % in minutes) before the market stabilizes.

2. Absence of continuous price‑discovery

   • During regular hours, price discovery is a continuous, competitive process: many participants submit bids and offers, smoothing out the impact of new data.
     
   • At 4 pm, the “continuous” process stops; the market must price‑discover in a single, discrete block (the after‑hours session). This tends to produce higher volatility as participants react at different speeds.

3. Potential “gap‑up” or “gap‑down” at the next open

   • If the after‑hours price settles far from the prior close, the opening auction can open with a sizable gap.
     
   • Example: If CMPS trades at $0.85 after the presentation versus $0.80 at the close, the next day may open at $0.86 (gap‑up) or $0.78 (gap‑down) depending on order‑book imbalances.

4. Algorithmic and “stop‑loss” cascades

   • Many algorithmic strategies (e.g., volatility‑targeting, stop‑loss, or “liquidity‑seeking” bots) are still active after‑hours.
     
   • A sharp move can trigger automatic sell or buy orders that further amplify the swing, especially when the spread is already wide.

5. Higher “price‑impact” per share

   • Empirical studies (e.g., Kyle’s model) show that price impact ∝ 1 / (liquidity). With liquidity down to ~10 % of regular‑hour levels, the impact per share can be 10× larger than during the last hour of the regular session.

4. Practical implications for different market participants

5. Historical reference points (for context)

These examples illustrate that a 4 pm information release can produce *single‑digit to double‑digit percentage moves** in a very short time frame, precisely because the market is operating with reduced liquidity.*

6. Bottom‑line take‑aways

1. Liquidity is thin at 4 pm – the regular‑session order book collapses, spreads widen, and market‑maker participation drops dramatically.
   
2. Price impact per share is magnified – a modest trade can move the price far more than it would during the last hour of the regular session.
   
3. Volatility spikes in after‑hours – the first 30‑60 minutes after the close are likely to see the most erratic price action, driven by a mix of institutional block trades, algorithmic stop‑losses, and the sheer novelty of the information.
   
4. Potential for a gap at the next open – the after‑hours price often sets the opening price for the following day, creating a gap‑up or gap‑down scenario that can be larger than typical overnight moves.
   
5. Strategic positioning matters – investors who want to capture the “information premium” may pre‑position before the close; those who wish to avoid the volatility should stay out of after‑hours trading and instead evaluate the news at the next day’s open.

TL;DR

Because the Compass Pathways presentation is slated for 4:00 pm ET, right at the market close, the new information will be digested in a low‑liquidity, after‑hours environment. This timing typically leads to wider spreads, larger price impact per trade, heightened short‑term volatility, and a possible opening‑price gap the next day. Market participants should therefore anticipate a sharp, compressed price reaction and plan their trading or risk‑management approach accordingly.