In plain words — Welles Wilder did not build one indicator that claims to explain everything. He separated four questions: how much the market moves, in which direction, with what intensity, and where a stop should advance.
John Welles Wilder Jr. (1935–2021) was an American mechanical engineer, real-estate entrepreneur and author. The CMT Association credits his 1978 book New Concepts in Technical Trading Systems with presenting a family of tools that later became standard technical-analysis vocabulary. In an interview republished by the association, Wilder himself described the book as his first success in the commodities field.
The book was designed around daily data, worksheets and explicit systems. That historical setting matters when its indicators are applied to different markets and frequencies today.
The documented contribution
True range extends the simple high-low range by including the distance from the previous close; its average becomes ATR. It measures volatility, not price direction.
Directional Movement compares upward and downward expansion. +DI and −DI describe relative direction, while ADX summarises movement strength without saying whether the trend is rising or falling. Separating strength from direction is one of the book's most durable conceptual choices.
RSI normalises the relationship between advances and declines on a 0–100 scale; the original setting uses 14 periods. Wilder also presented extremes, divergences and chart patterns on the oscillator, but these readings are not self-sufficient signals.
Parabolic SAR is instead a stop-and-reverse procedure: the stop accelerates as the trend continues and the system reverses when price reaches it. ATR, DMI/ADX, RSI and SAR share an author and publication context, but they measure different objects and do not automatically form one strategy.
Limits and attribution
Platform implementations can differ in initialisation, rounding, smoothing and the treatment of missing data. Fourteen is a historical parameter, not a universal constant. Moving a rule from 1978 daily commodities to equities, crypto assets or intraday data requires fresh validation.
A CMT Association review notes that the original RSI examples were not equivalent to broad out-of-sample statistical testing. An indicator's popularity does not prove that a threshold produces returns. Moreover, high ATR does not mean trend, high ADX does not reveal direction, and “overbought” RSI does not imply an immediate reversal.
What to study today
Start by reconstructing each tool's question, then its calculation and finally the decision it is meant to support. Test ATR for sizing and stops, ADX as a regime filter, RSI as a momentum description, and SAR as an exit rule. Parameters, costs, universe and test period must be stated: an indicator becomes a method only within a complete risk and validation process.
Sources
- J. Welles Wilder Jr., New Concepts in Technical Trading Systems, Trend Research, 1978 — primary work held by the University of Macedonia repository.
- Stuart McPhee, “J. Welles Wilder”, CMT Association, August 2006 — interview with Wilder on the book's origin and its systems.
- Michael Carr, “Relative Strength Index”, CMT Association, February 2013 — original RSI context and limits of the initial evidence.
- Michael Kahn, “In Memoriam — J. Welles Wilder, Jr.”, CMT Association, May 2021 — biographical profile and contribution catalogue.