Mystery solved: The discrepancy in homicide data

on Jul 27, 2010
I've been complaining about how homicide statistics from police sources were too low in 2009, with the entire state of Chihuahua having less homicides than its biggest city. I was thinking of finding out if I could use the IFAI (Freedom of Information Access) to obtain the original CIEISP forms which the state police forces are supposed to fill out each month and send to the National System of Public Security (SNSP) for tallying, to see if there were any unusual patterns, but someone beat me to requesting the data.

You can see the request here, and download the excel file with the CIEISP forms here.

The main difference between the datasets is that the CIEISP forms usually report lower numbers than the data the SNSP gave to the ICESI. This is not surprising since the CIEISP forms have no recorded homicides in some states during the last months of the year (the request was made in December 2009), but the numbers for Chihuahua in both datasets are identical, with a total of 2523 homicides recorded. More importantly, in the months of November and December there were no homicides registered in the CIEISP forms, and the data for October looks incomplete. That's the reason Chihuahua had such a low homicide rate according to the police, the data they gave to the ICESI only includes 9¾ months of homicides.

Homicide in North America

on Jul 14, 2010

I'm surprised by how similar the trends are (excluding the drug war in Mexico). There were big decreases in the homicide rate in all three countries starting in the early nineties, which then slowed down around 2000.

The municipalities with the highest and lowest homicide rates by sex

on Jul 9, 2010
The municipalities are ordered by their peak homicide rate and the dotted gray line is the average homicide rate over the 2005–2008 period. Since homicide is mostly a male phenomenon it's not surprising to find Ciudad Juarez is the most violent city for men.