The XUB indexes highlight extreme short term behavior. Separate indexes are maintained for NYSE and Nasdaq. The XUBs are based on price action of the highest-energy stocks that are specifically excluded from the Core indexes.
XUB carries two kinds of directional inference. Extreme values (positive or negative) often indicate imminent minor reversals, and divergence from price trends often indicate growing intermediate strength or weakness. These indexes date fro the end of 1999. A recent year of Nasdaq XUBerance is shown here....
Following is a five-year look at the NYSE XUBerance, with occasions marked where XUB moves up through levels of +.3883 (an arbitrary example of a "high" reading). There were ten such occasions over the five years. The graph shows how extreme XUB readings tend to precede soon correction of uptrend.