The terms phylogenetic efficiency and phylogenetic accuracy have often been confused in the literature. Accuracy is a measure of truth while efficiency is the ratio of computer time devoted to conduct an analysis to the frequency that optimal trees are obtained. It has been argued, using an empirical example, that additional character data will actually decrease the overall analysis time and therefore increase efficiency. Although this example claimed a decrease in the time required for a tree search, the success or failure of each tree search was not accounted for. Thus, this example did not in fact demonstrate an improvement in efficiency. For our study the three gene angiosperm matrix (567 taxa; rbcL, atpB, and 18S sequence) was used as a model data set. We found: (1) Not all methods of analysis have the same success rate. The types of traditional searches that can be completed in a "reasonable" amount of time have a near zero success rate and therefore are totally inefficient while non-traditional methods (e.g. the parsimony ratchet) are much more efficient. (2) There is no one method that is most efficient for all data sets. In some cases tree fusion is much more efficient than the ratchet (18S) while in other cases the reverse is true (rbcL, atpB). (3) The pattern of homoplasy within a data set has a greater impact on the efficiency of analysis than the number of characters. (4) Since additional characters slow the analysis (the increase is linear) the only way additional characters can make the analysis more efficient is if the characters increase the decisiveness of the data.

Key words: analysis, cladistic, efficiency, phylogenetic, speed, tree search