Follow-through Day

Follow-through Day, also known as FTD, follow-through, IBD follow-through day, is a Breadth, Sentiment & External Data concept. The Library holds 1 implementation, a working definition you can pull into Quant.

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Follow-through Day

Indicator

What is a follow-through day?

A follow-through day is William O'Neil's confirmation that a market correction may have ended: on the fourth day or later of a rally attempt, a major index closes up strongly on higher volume than the session before. It is the bullish half of the market-direction rules in O'Neil's How to Make Money in Stocks, applied daily by Investor's Business Daily, and the counterpart to the distribution day count.

The counting is precise. Day 1 of a rally attempt is the first session after a new correction low in which the index closes higher; IBD also accepts a day that undercuts the low and then closes in the upper half of its range. The attempt stays alive while the index holds above Day 1's low; an undercut restarts the count. From Day 4 onward, a gain of at least a set percentage in the Nasdaq Composite or the S&P 500, on volume above the prior session, is the follow-through; one index is enough. O'Neil found the strongest follow-throughs on days 4 to 7.

The minimum gain has moved over the decades. O'Neil's original rule used 1%, and his 2002 edition says he had since raised it; IBD was applying 1.7% by the mid-2000s, arguing markets had grown more volatile, and recent descriptions of IBD's rule commonly give about 1.25%. The volume test has not changed: higher than the day before, not necessarily above average.

IBD's position is that not every follow-through leads to a new uptrend, but no major rally has begun without one. Independent tests are mixed: Rob Hanna's 2008 Quantifiable Edges studies of S&P 500 follow-throughs since 1971 found success rates near a coin flip under his definitions, short of the 70 to 80 percent IBD had cited, and found the 1.7% bar missed or came late to several rallies the 1% version caught. Treat it as permission to start buying leaders, not as a buy signal for the index.

How it's calculated

Rally-attempt counting and the follow-through test on one index's daily data.

rt=100×Ct−Ct−1Ct−1r_t = 100 \times \frac{C_t - C_{t-1}}{C_{t-1}}
Day 1=first session d after the correction low with Cd>Cd−1\text{Day 1} = \text{first session } d \text{ after the correction low with } C_d > C_{d-1}
nt=t−d+1n_t = t - d + 1
Alive⁡t=1 if min⁡(Ld+1,…,Lt)≥Ld, else 0\operatorname{Alive}_t = 1 \text{ if } \min(L_{d+1}, \ldots, L_t) \ge L_d\text{, else } 0
FTD⁡t=1 if Alive⁡t=1, nt≥4, rt≥θ, and Vt>Vt−1, else 0\operatorname{FTD}_t = 1 \text{ if } \operatorname{Alive}_t = 1,\ n_t \ge 4,\ r_t \ge \theta, \text{ and } V_t > V_{t-1}\text{, else } 0
C_t: index close on day t
L_t: index low on day t
V_t: index volume on day t
r_t: daily percentage change of the close
d: the session that starts the rally attempt (Day 1)
n_t: rally-attempt day number on day t
Alive_t: 1 while the attempt has not undercut Day 1's low
θ: minimum gain in percent (1 in the original rule, 1.7 in IBD's 2000s rule, about 1.25 in recent descriptions)
FTD_t: 1 when day t is a follow-through day
t: trading-day index

Run the test on the Nasdaq Composite and the S&P 500 separately; when Alive_t drops to 0, a new Day 1 is sought.

How traders use it

  • Re-entry permission: O'Neil-style traders wait for a follow-through before buying, then add exposure only as leading stocks break out of sound bases and hold.
  • Gradual exposure: positions are built in steps after the signal, so a failed follow-through costs a small test position, not a full book.
  • Failure monitoring: an undercut of the rally attempt's low, or distribution days stacking up soon after the signal, puts the market back in correction.

Follow-through day vs related signals

Distribution Day Count: The bearish counterpart: high-volume down days counted over 25 sessions. A follow-through is a single event confirming a new uptrend; distribution days accumulate to question an existing one.

Breadth Thrusts: A thrust measures how fast participation swings from washed out to near-unanimous across many stocks. A follow-through uses only the index's change and volume, so it can fire on a narrow rally.

O'Neil Base Analysis: Base analysis times entries in individual stocks. The follow-through day decides whether the market environment permits those entries at all; O'Neil's method uses the two together.

Concept family

Breadth, Sentiment & External Data

56 concepts mapped · 56 in the Library

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