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Effective spread split into realized spread and adverse selection, by half hour

Answered against 22 years of US equities and 12 years of US options data and published with the query that produced it. This result is stored as of 2026-08-15, from Trade Markouts Explained: Execution Quality.

as of series 13×5read in context →
Effective spread split into realized spread and adverse selection, by half hour — 13 rows by 5 columns, computed from US exchange, SIP and OPRA data.
et_timeeffective_spread_bpsrealized_spread_bpsadverse_selection_bpsfill_count
09:3010.6512.3388.313156976
10:008.0531.8926.16193545
10:307.573-9.09116.66595266
11:007.0791.6665.41487234
11:307.704-4.86412.56869850
12:005.6243.9181.70748500
12:305.1510.0385.11245567
13:004.6670.9323.73539236
13:305.598-0.0345.63243249
14:004.59-1.1345.72338018
14:304.5041.2563.24948662
15:005.29-1.6156.90564389
15:306.184-1.087.26569101
Rows × columns
13 × 5
Period covered
to
Computed
Completeness
No missing values
Source
US exchange, SIP and OPRA market data
Licence
Strasmore terms · free, no signup
Formats
JSON · CSV · the SQL below

What each column holds

Column definitions for Effective spread split into realized spread and adverse selection, by half hour, derived from the stored result.
ColumnTypeRangeNotes
et_time date 09:30 to 15:30
effective_spread_bps number 4.504 to 10.651
realized_spread_bps number -9.091 to 3.918
adverse_selection_bps number 1.707 to 16.665
fill_count number 38,018 to 156,976 count

Computed from Strasmore's warehouse of US exchange, SIP and OPRA market data. Equity prices are delayed; options greeks and implied volatility are end-of-day. This result is stored, not recomputed on load — it is exactly the numbers that were returned on , and the query below is what returned them.

the exact SQL behind every number
WITH
    mid_by_second AS
    (
        SELECT
            dateDiff('second', toDateTime('2026-06-10 13:30:00', 'UTC'), sip_timestamp) AS sec,
            argMax((toFloat64(bid_price) + toFloat64(ask_price)) / 2, sip_timestamp)    AS mid
        FROM global_markets.cache_stocks_quotes
        WHERE ticker = 'INTC'
          AND sip_timestamp >= toDateTime('2026-06-10 13:30:00', 'UTC')
          AND sip_timestamp <  toDateTime('2026-06-10 20:00:00', 'UTC')
          AND bid_price > 0
          AND ask_price > bid_price
        GROUP BY sec
    ),
    signed_fills AS
    (
        SELECT
            t.sec + 60   AS future_sec,
            t.et_time    AS et_time,
            t.fill_price AS fill_price,
            q.mid        AS ref_mid,
            if(t.fill_price > q.mid, 1, -1) AS side
        FROM
        (
            SELECT
                dateDiff('second', toDateTime('2026-06-10 13:30:00', 'UTC'), sip_timestamp) AS sec,
                sec - 1          AS ref_sec,
                toFloat64(price) AS fill_price,
                formatDateTime(toStartOfInterval(toTimeZone(sip_timestamp, 'America/New_York'), toIntervalMinute(30)), '%H:%i') AS et_time
            FROM global_markets.stocks_trades
            WHERE ticker = 'INTC'
              AND sip_timestamp >= toDateTime('2026-06-10 13:30:01', 'UTC')
              AND sip_timestamp <  toDateTime('2026-06-10 19:55:00', 'UTC')
              AND price > 0
              AND size > 0
        ) AS t
        INNER JOIN mid_by_second AS q ON q.sec = t.ref_sec
        WHERE t.fill_price != q.mid
    )
SELECT
    f.et_time                                                                  AS et_time,
    round(avg(2 * f.side * (f.fill_price - f.ref_mid) / f.ref_mid) * 10000, 3) AS effective_spread_bps,
    round(avg(2 * f.side * (f.fill_price - fut.mid) / f.ref_mid) * 10000, 3)   AS realized_spread_bps,
    round(avg(2 * f.side * (fut.mid - f.ref_mid) / f.ref_mid) * 10000, 3)      AS adverse_selection_bps,
    count()                                                                    AS fill_count
FROM signed_fills AS f
INNER JOIN mid_by_second AS fut ON fut.sec = f.future_sec
GROUP BY f.et_time
ORDER BY f.et_time

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