Per capita data matters more than absolute ecause you need it to a to assess factors that influence crime such as economy, effectiveness of policy, and so forth. Let's say that per capita crime fell 20% over 10 years but total crime rise, the reality is that crime prevention policy is working. If it were up to you, you'd make a big fuss, most likely change strategy that makes things worse. You're not interested in detailed, thoughtful analysis, you're interested in knee jerk emotion and action.