Thursday, May 24, 2012

Reporting Without Thinking

This is National Dog Bite Prevention Week, so the U.S. Postal Service put out a list of cities with the greatest number of dog attacks on mail carriers. The Chicago Tribune picked up the story and apparently couldn't be bothered to do ten seconds of critical thinking before blurting out "Postal Service ranks Chicago high for dog attacks." My first thought was, No wonder our mail carrier always jumps back when we open the door. But that isn't the real story at all.
There were 30 dog attacks on postal workers last year in Chicago. That puts Chicago at No. 11, tied with Philadelphia. Los Angeles topped the list with 83 dog attacks on postal employees last year.
Notice that the article is about the total number of attacks per city rather than, say, attacks per postal customer or per capita. Chicago is the third most populous city in the United States. If Chicago is ranked eleventh, that means there many cities with fewer people that had a higher number of attacks. I found a complete list of the "top 25" (actually there are 43 cities listed*). Here is part of the list:

Ranking
City/Location
Attacks
1
Los Angeles, CA
83
2
San Diego, CA
68
3
Houston, TX
47
4
Cleveland, OH
44
5
Dallas, TX
41
6
San Antonio, TX
39
7
Phoenix, AZ
36
8
Denver, CO, and Sacramento, CA
35 each
9
Minneapolis, MN, and St. Louis, MO
32 each
10
Louisville, KY
31
11
Chicago, IL, and Philadelphia, PA
30 each
12
Seattle, WA
28
In fact, there are twelve cities ahead of Chicago, and all but one are smaller, some of them significantly so. Chicago has about 2.7 million people, while cities like Cleveland, Minneapolis, and St. Louis come in under 400,000. In other words, Chicago is actually a pretty safe place for mail carriers!

Note: I'd like to show you bites per capita, but I'm not very good with tables in Blogger (the only reason I used the table above is because I copy/pasted from another site). Here is a list of U.S. cities ranked by population.


* Normally, if two cities tie for second place, one would expect the next city to be ranked fourth. But on this list, the next city would be third. Because the numbers of attacks are relatively low to begin with, there are a lot of ties, resulting in a lot more than 25 cities represented on the list.

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