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Heat List: Correlation or Causation 

From the Tribune

The heat list is in the news again: 

Just last week, after the bloodiest weekend since he became superintendent, Eddie Johnson said much of the bloodshed is being driven by about 1,300 people on the list, compiled with the aid of a computerized algorithm.

Calling the initiative the Police Department's "largest raid in recent history," Anthony Guglielmi, the department's chief spokesman, said 140 people were arrested primarily on narcotics and weapons charges starting at 4 a.m. Thursday in the violence-plagued Harrison and Austin patrol districts on the West Side.  Police were targeting the Traveling Vice Lord and Four Corner Hustler street gangs in the crackdown. About 95 documented gang members were arrested, Guglielmi said.  In addition, all but 23 of those arrested Thursday were on the strategic subject list, police officials said.

"Those individuals need to know that if they don't choose to take an alternative lifestyle then we'll bring everything we have at our disposal, including our federal partners to come at them to put the weight of the Chicago Police Department on them to stop them from driving the violence in our city," Johnson said at a news conference Friday at police headquarters.

The algorithm used in compiling the list ranks the individuals on their susceptibility to violence. Some of those factors are their criminal background, their parole or warrant status, and any weapons or drug arrests. The department also takes into consideration their known acquaintances — and the acquaintances' arrest histories — and whether any of those associates have been shot in the past.

Police said 21 of those arrested in the raid have been calculated to be at least 300 times more likely than the average person to become a victim or offender of violence.

As far as I know, this is the first time the city has discussed the heat list so prominently for arrests.  A couple of quick reactions, first it’s not clear whether the arrests are correlated to the heat list or caused by the heat list. Simply, were arrests made on the basis of predictions?  Or is there a correlation between people who were arrested and being on the heat list? This will grow to be an important distinction, because eventually arrests could be based on the heat list.

Second, lets run the numbers here, 1300 people are on the list.  This weekend they arrested 140 people.  16% of those people were not on the heat list (23/140). 68% of the people arrested were known gang members (95/140).  This means 16% of the heat list people were not affiliated with a gang (of those arrested this weekend).  This gives a little insight into the makeup of the list.  Finally, what is the lasting effect of arrests based on weapons and/or narcotics?  How long will these people be off the street?     

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    Eyeing Chicago - Eyeing Chicago - Heat List: Correlation or Causation

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