 First, the structure of adjudication does not generally provide adequate or appropriate information for the selection of rules that maximize social welfare. Adjudication in a common law system usually focuses on a past transaction between particular parties. This transaction may not be typical of transactions that were litigated; it certainly will not be typical of the entire population of transactions that a rule would govern. Under a given rule, for instance, the set of transactions that do not lead to litigation are likely to differ systematically from the set of transactions that do give rise to litigation. Equally important, different legal rules are apt to generate different sets of transactions. The current structure of adjudication does not provide any information that would help a decision maker assess these differences across potential legal rules.