Friday, May 4, 2012

Accurate Crime Statistics Matter

The Visalia Times-Delta had a recent story about Tulare, California Police Department's efforts to ensure their crime statistics are accurate.

"You have to know you produce valid data," she said. "That information must be reliable. It has to be accurate."

Faulty information can send law enforcement agencies the wrong direction when dealing with a crime wave or be late in reallocating resources to handle hard-to-spot trends.

One illustration I frequently use when I speak to the public about crime analysis and the importance of accuracy is comparing crime statistics to dead reckoning navigation. Back in the days before modern navigation devices, sailing ships used this method of navigation to get where they were going.

The way it worked was ships would start from a known position, then carefully chart their direction, speed and time traveled to determine where they were at all times so they could get to where they were headed.

In applying this analogy to crime analysis, in order to know where you are going, you have to know as accurately as possible where you have been. If you are going to know if your crime reduction efforts are effective, you need to maintain accurate crime statistics at all times.

What are you doing to encourage a culture of accurate crime statistics within your agency?


  1. Hi Scott,

    Great points. After working at my agency for the past couple of years, I've begun to realize the intricacies of our RMS, missing/miscoded data, and data quality. I understand that statistics will change, e.g., details are updated because of investigations, legislative changes, etc. However there needs to be vigilant reviews of our data (both from the entry and maintenance side).

    What I'm doing is writing up a memo to my supervisors about data accuracy. I hope to conduct a presentation for members from all levels of my agency to stress that analytical products are only as valid as the data that is entered; essentially reiterating the point of "garbage in, garbage out".

    I will also be outlining internal structures and mechanisms showing the flow of data from data entry/collection to data maintenance, in an attempt to identify weaknesses and improvements. These obstacles will clearly affect the products that I produce, decisions made by upper management, and ultimately the effectiveness of our agency & the safety of our community.

    Analysts should be constantly creating information from the data, so we need cooperation from all levels to ensure data accuracy. We also need to illustrate the importance of "numbers" being more than just statistics; it's also about actual analysis, not just about describing the data, but providing knowledge for actionable solutions.

    John Ng

  2. John, Great observations! Thanks for the comment.

  3. There are some great resources at and also on accurate crime stats. This is an issue I am passionate about.


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