Itemset share, the fraction of some numerical total contributed by items wh
en they occur in itemsets, has been proposed as a measure of the importance
of itemsets in association rule mining. The IAB and CAC algorithms are abl
e to find share frequent itemsets that have infrequent subsets. These algor
ithms perform well, but they do not always find all possible share frequent
itemsets. In this paper, we describe the incorporation of a threshold fact
or into these algorithms. The threshold factor can be used to increase the
number of frequent itemsets found at a cost of an increase in the number of
infrequent itemsets examined. The modified algorithms are tested on a larg
e commercial database. Their behavior is examined using principles of class
ifier evaluation from machine learning.