If we consider all the trust relations we experience, we find that a large fraction of them fall into three categories: relationships or interactions that are iterated, those that are backed up by institutions, and those that are mediated by other (noninstitutional) third parties. This chapter has focused on the first of these categories. … The first category—iterated interactions—seems to be far and away the largest in ordinary interpersonal life. That is because much of our lives is spent in ongoing relationships, such relationships constitute much of what is most valuable to us, and we make substantial commitments to one another in such relationships.

Russell Hardin, Trust and Trustworthiness, loc. 155