The most obvious ones occur in cases where you detect a trend. People who don't know each other, who are geographically apart, come forward with the same experience. This discloses to you that there is a systemic problem, a problem that lies beyond an individual case or decision. That's the most obvious case. But we also have cases where very few complaints may disclose a systemic issue. So trends are not always the rule, but they're the safest rule.
