William Eckhardt: The Man Who Launched 1,000 Systems

All credit to www.futuresmag.com/Issues/2011/March-2011/Pages/William-Eckhardt-.aspx?page=1

Futures Magazine: Many in the traditional investment world cling to the notion that markets are efficient. Trend-following is not valid under the efficient market hypothesis (EMH) but here you are 30 years later. Why has the EMH persisted? Talk about this anomaly.

Bill Eckhardt: The random walk model of price change has been so durable because it’s nearly correct. The difference between futures prices and certain random walks is too small to detect using traditional time series analysis. Incredibly, this difference is detectable using trading systems.

FM: How do trading systems do this?

BE: Trading systems can be highly sensitive to non-linear relations in price series. So why doesn’t this revolutionize the modeling of price series? Statistical estimators probe particular features of the price series; they are equipped with confidence levels, give information about possible models, and are useful for prediction. From the point of view of the modeler, trading systems do not locate specific features of the price series; they have no confidence levels and are useless for prediction.

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