In 2002, Paul Desmond won the 2002 Charles H. Dow Award for his work in identifying market bottoms and new bull markets. Since this work nicely supports Wyckoff's hypotheses regarding selling climaxes, technical rallies, and "secondary reactions", or tests, I've posted Desmond's study below in pdf form. I've also excerpted several points which are particularly pertinent to Wyckoff's aforementioned hypotheses and which will act as an introduction to the study. Please note that all bolding is mine.
To spot an important market bottom, almost as it is happening, requires a close examination of the forces of supply and demand – the buying and selling that takes place during the decline to the market low - as well as during the subsequent reversal point. Important market bottoms are preceded by, and result from, important market declines. And, important market declines are, for the most part, a study in the extremes of human emotion. The intensity of their emotions can be statistically measured through their purchases and sales.
[P]anic selling must be measured in terms of intensity, rather than just activity.
It is essential to recognize that days of panic selling [in which Downside Volume equaled 90.0% or more of the total of Upside Volume plus Downside Volume, and Points Lost equaled 90.0% or more of the total of Points Gained plus Points Lost] cannot, by themselves, produce a market reversal, any more than simply lowering the sale price on a house will suddenly produce an enthusiastic buyer. As the Law of Supply and Demand would emphasize, it takes strong Demand, not just a reduction in Supply, to cause prices to rise substantially....These two events – panic selling (one or more 90% Downside Days) and panic buying (a 90% Upside Day...) – produce very powerful probabilities that a major trend reversal has begun….
Not all of these combination patterns – 90% Down and 90% Up – have occurred at major market bottoms. But, by observing the occurrence of 90% Days, investors have (1) been able to avoid buying too soon in a rapidly declining market, and (2) been able to identify many major turning points in their very early stages – usually far faster than with other forms of fundamental or technical trend analysis.
Impressive, big-volume “snap-back” [technical] rallies lasting from two to seven days commonly follow quickly after 90% Downside Days, and can be very advantageous for nimble traders. But, as a general rule, longerterm investors should not be in a hurry to buy back into a market containing multiple 90% Downside Days, and should probably view snapback rallies as opportunities to move to a more defensive position.
The following is of course a chart of the Nasdaq over the past few months up through yesterday and is intended as an example. The calculations are not guaranteed to be accurate. Anyone caring to verify them and point out any errors is welcome to do so. Readers are encouraged to read the study in its entirety.
2002DowAward.pdf