“Another situation in which we attend to base rates occurs if people ascribe some causal significance to discrepant rates. When they can see the causal relevance of the base rates, they often incorporate them into their reasoning. For example, the belief that one bus company has more accidents than another because its drivers are more poorly selected and trained will influence mock jurors to take this difference in accident rates into account in evaluating eyewitness testimony; but belief that a bus company has more accidents simply because it is larger will not. Study after study has shown that when these rates are merely statistical as opposed to causal, they tend to be ignored. Exactly the same effect seems to occur in real courtrooms; naked statistical evidence is notoriously unpersuasive.”