Tag Archives: crime

more numbers on Philadelphia shootings

Leave a reply

A report commissioned by the Philadelphia has some facts and figures on shootings, both fatal (the layman might refer to these as “murders”) and non-fatal. Here are just a few that caught my eye:

  • For every fatal shooting, 3-4 people are shot non-fatally
  • Arguments are cited as the cause of 50% of shootings, while drug-related issues are cited in 18%. (My thinking on this is slowly evolving, because previously I had assumed the drug economy was at the root of much of the violence. I still wonder if the drug economy factors in some way into many of the arguments if you trace them back far enough, and maybe arguments just take on a life of their own at some point.)
  • 37% of fatal shootings from 2020 have been cleared as of January 2022, where “cleared” generally means an arrest has been made. I wondered how many cases might still be open from 2020 that might still be cleared, but the report says that when an arrest is going to be made, 75% of the time it will be made within about three months.
  • Conviction rates in fatal shooting cases ranged from 96% in 2016 to 80% in 2020.

The book Ghettoside referred to a 40% clearance rate in Los Angeles during the height of the 1990s murder surge there. It is remarkable how similar the 37% number above is. Doing the math, the chances of a murderer being caught and convicted is something like 1 in 3. Again, in a surprising echo of what that book discussed, the recommendations of this report mostly talk about crime prevention and suppression strategies. They specifically talk about dedicating more resources to investigation of non-fatal shootings, but they do not recommend increasing the number of homicide detectives or improving their training.

Ghettoside

Leave a reply

I’m reading Ghettoside: A True Story of Murder in America, a book about homicide in Los Angeles between the late 1980s and early 2000s. The word “ghetto”, by the way, might seem loaded but it is how residents and police referred to the neighborhood that is the focus of the book. It’s a very interesting and also disturbing book. It tells a little bit different story than what I have been reading in books and the media elsewhere. In the view of this book, a central factor in high homicide rates, at least in Los Angeles at the time covered in the book, is that police departments don’t solve murders of black men and boys at the same high rates that they solve murders of other groups. This leads to a situation of lawlessness where a sort of “law of the street” develops. In this view, people would actually like more help from the authorities if they felt it was fair and professional, but they don’t believe they can get it so they take matters into their own hands.

The book talks about disputes and arguments among men and boys getting out of hand and leading to cycles of revenge and retaliation. Homicide detectives do their best, but even the best homicide detectives have limited capacity, and training new ones is difficult. When there is a spike in homicides, the supply of good homicide detectives does not increase in kind. Cases get rushed and a smaller fraction of the total get solved. People correctly learn that they are likely to get away with murder, and that contributes to the feedback loop. In Los Angeles at the time, the situation escalated to the point that total strangers were murdering each other simply for being in the wrong neighborhood or wearing the wrong color clothing.

The book argues that Los Angeles at the time was diverting resources from investigating and solving homicides to “violence prevention” and “predictive policing” programs, which were politically popular but less effective than simply solving more cases would have been. It also argues that people can feel harassed and overpoliced at the same time they might support more investigation and solving of violent crime cases if they felt it was fair and effective. I hear echoes of this in the media during the current homicide wave we are experiencing in many U.S. cities. Maybe the violence prevention approaches have improved and have more evidence behind them, but we do hear both that homicide is way up and that the clearance rate is down. And we perpetually hear about the idea of a lack of trust and respect between police and residents of primarily black neighborhoods.

It’s interesting that the crimes discussed in the book are almost all gun crimes, but this is not a book that focuses on guns. Nor does it focus on the drug trade. It focuses on the people involved and their motivations on all sides, from victims to perpetrators to police. It mentions a few police shootings of suspects in passing, but this is also not a focus of the book.

Philadelphia homicides in 2021

Leave a reply

The Philadelphia Inquirer has a decent piece of data journalism on the shocking number of homicides in our city in 2021. Here are some numbers:

  • 557 homicides as of Wednesday, December 29, so we will probably add a few more by midnight on New Year’s Eve.
  • This eclipses the previous record of 500 in 1990. The period 1989-1997 consistently had over 400 homicides per year. We have now had two years in a row in the 500+ range (499 in 2020). During the 2009-2019 decade, the range was 246-356.
  • Guns were the cause of death in 89% of homicides. Nationwide, this number is around 75%.
  • Of the 557, 111 (20%) were considered retaliatory, 166 (30%) were drug related, and 42 (8%) were domestic violence related. It is not entirely clear to me if these percentages overlap or not – hence my giving this article a grade of only “decent”.
  • 8 of the 10 most populous cities in the U.S. recorded more homicides as of December 29, 2021 than they did in 2019. New York City has had 479 murders this year and Chicago “nearly 800”. The article doesn’t normalize these by population for us but I can do that.
    • Philadelphia: 557 homicides / 1.579 million people = 352 per million
    • New York City: 479 homicides / 8.419 million people = 57 per million
    • Chicago: ~800 / 2.71 million people = 295 per million

Philadelphia Inquirer, to go from decent to good, just put these numbers in a nice table or bullet list for us and normalize by population. Bonus points for some kind of bar chart of “tree map” that makes it crystal clear what the categories are and whether any overlap. “Communities of color” are mentioned but there are no numbers on the breakdown of victims or perpetrators by race or by age (they do mention that the number of female victims has increased, although victims remain overwhelmingly male).

So despite the eye-popping numbers in Chicago, Philadelphia is a bit worse although the two are similar. New York is doing much better.

There is a lot of hand wringing over the causes of violence. It is crystal clear though that plentiful guns make disputes and arguments much more deadly than they otherwise might be. Beyond that, we know the pandemic resulted in a large population of teenage boys out of school for a year and a half. We know the pandemic led to an increase in the unemployment rate.

Those are some facts. Now to speculate. The unemployment rate measures the formal economy, but we know that people who are unemployed in the formal economy are not necessarily economically idle. We can speculate that more people, particularly young men, became involved in the drug economy during the pandemic. Mix together young men, drugs, cash, guns, and a culture that leads to cycles of retaliation and revenge, and it is easy to picture a feedback loop that could get out of control.

It’s interesting that many categories of crime are down. This is at least partly because the police are not pursuing nonviolent crimes as much, particularly drug use and drug possession. Many people are drawing a link between decreased enforcement and increased homicides. “Homicide” and “crime” are often used interchangeably in the media, but this is wrong. Homicides are a tiny fraction of crime as a whole, and crime as a whole is down. Reduced enforcement could easily be a reason that crime as a whole is down.

How would you break the homicide loop? Media coverage focuses on guns, and reducing the number of guns might help, but that is very hard to do in our “exceptional” country. Legalizing drugs would take away the profits and economic incentive to traffic drugs and deal drugs, reduce the amount of cash changing hands, and very likely reduce the level of violence caused by drug dealers defending themselves from each other. Assuming this is what touches off many of the retaliation cycles, those should also decrease. Drug addiction might or might not increase, I am not sure, but that could be treated as the medical/behavioral problem it is. The violence on our city streets (not to mention horrific violence to get drugs across our international borders) is just not an acceptable price to pay to reduce the social problems caused by drug use, if the prohibition and law enforcement strategy was even working, which it is clearly not.

So longer term, after legalizing drugs, logical strategies would be an actual public health care system able to help people with addiction, and education and training of young men so they have economic opportunities in the formal economy. Our political system has repeatedly failed to provide these things, partly because rural politicians and voters have disproportionate political power and like to believe poverty, drugs, and violence affect only the mythical “inner city”.

mass incarceration

Leave a reply

Maybe I’ve finally put my finger on what bothered me about Black Lives Matter. Of course I’m not in favor of police brutality and nobody should be. Police brutality is a huge problem for the people on the receiving end of it, and it needs to be addressed. Addressing it would only remove drop from the bucket of violence and injustice in this country. We need to identify and address root causes of violence and injustice, but maybe that is too vague a concept for people to be marching in the streets about. Mass incarceration is concrete – we hear the numbers frequently, the U.S. has 5% of the world’s population and 25% of the world’s prisoners. For every 100 or so people you see walking on the street, there is one American in a federal, state, or local jail. And some of those people on the street are on probation and parole. Add in friends and family of all those people, and a huge proportion of the population is affected, certainly enough to get a march together.

So what can we do about it? Just trying to reason it out, I would first identify things that don’t need to be crimes, and don’t make them crimes any more. Drug use and possession come to mind – unless you are selling drugs to children, you are really only hurting yourself and/or other consenting adults, and this should be dealt with through the health care system (we need a health care system!). Go ahead and legalize prostitution. Gambling is pretty much legal already. There might be other things in this category I haven’t thought of. Next, find non-violent ways to treat non-violent crimes. For example, address property crimes by taking away property.

Finally, you come down to just violent crimes, and violent criminals do need to be taken off the streets. But you can try to find ways to reduce and prevent crime rather than just treat the symptoms. Ultimately, as suggested in this Brennan Center for Justice report, the answer is to look at all those approaches and programs that have been tried on a small scale, follow the evidence, and then try to scale up the ones that have been proven to work. Things that have been tried include “deferred-sentencing diversion programs, pre-booking diversion programs, and alternative court models, including mental health and drug courts.”

This is hard, but unlike say, education, mass incarceration is pretty easy to measure and determine if we are making progress or not.

predictive policing

Leave a reply

Here’s an interesting article on predictive policing from Motherboard. People are concerned that if a particular area has been overpoliced in the past, that is where the algorithms are going to predict crime in the future and they will continue to be overpoliced. Others just don’t like the idea of proprietary algorithms. I think any of these concerns could be badly depending on how it is implemented, but I don’t see why the tool itself could not be implemented in a fair way. In fact, I don’t see why measures to prevent discrimination couldn’t be built into the algorithms themselves. If the algorithms say people in a particular area or in a particular demographic group are being arrested at higher rates, it could help the search for route causes and preventive measures to help a particular group revert back to the mean. Transparency seems good in principle, maybe publishing some generalized statistics and maps, but of course if it is too predictable exactly where the police are going to be and when, people could take advantage of that. You could try to get around this by balancing random and targeted patterns within the algorithm.

U.S. murder rate down a bit

Leave a reply

In a bit of good news, the murder rate in the U.S. appears to be down this year compared to trends in the last several years, according to the New York Times.

In the cities in which data is available, murder has been down about 7 percent on average this year relative to the same point in 2017…

If murder falls about 4.5 percent nationally this year, the murder rate of about 5 per 100,000 will roughly be in line with 2009’s rate and half of what it was in 1980, the highest U.S. murder rate on record. The accompanying chart shows what the national murder rate since 1960 would look like with a 4.5 percent drop in 2018.

Tracking the change in murder nationally is far easier than explaining why it’s happening. There is still no consensus on why murder rose nationally in 2015 and 2016, though various theories have been proposed, including simple randomness. Similarly, a projected drop in murder in 2018 would not have an obvious cause. Employment of smarter technologies, expanded community intervention programs, and even colder weather could help explain year-to-year local changes.

If I had to speculate, it might be that the drugs in question in the current round of the war on drugs are simply not as lucrative, and therefore not as worth killing for, as the ones we saw in the 1990s. The real profits accrue to the people willing to take big risks to get the drugs across the border, and it could just be that the body count this time around has been shifted just outside the U.S. border. It may also be that the U.S. government at various levels has shifted toward a little more of a public health approach and a little less of a law enforcement approach. I could think positive and consider this progress, or I could be cynical and say it is partial because there is a wider range of ethnic and socioeconomic groups being affected this time around.

police officers accidentally film themselves planting evidence

Leave a reply

According to the Intercept,

Last month, the city public defender’s office discovered body camera footage showing a local cop placing a bag of heroin in a pile of a trash in an alley. The cop, unaware he was being filmed, walked out of the alley, “turned on” his camera, and went back to “find” the drugs. The cop then arrested a man for the heroin, placed him in jail. The man, who couldn’t afford to post the $50,000 bail, languished there for seven months. He was finally released two weeks ago, after the public defender’s office sent the video to the state attorney.

So, I think I support the body cameras, I don’t really see why honest police officers wouldn’t support them too. Maybe they shouldn’t even have an “off” button.

eyes on the street

Leave a reply

A group at the University of Pennsylvania looked for statistical evidence that “eyes on the street” are a deterrent to crime. The results are a bit puzzling, as real world data often can be.

ANALYSIS OF URBAN VIBRANCY AND SAFETY IN PHILADELPHIA

Statistical analyses of urban environments have been recently improved through publicly available high resolution data and mapping technologies that have adopted across industries. These technologies allow us to create metrics to empirically investigate urban design principles of the past half-century. Philadelphia is an interesting case study for this work, with its rapid urban development and population increase in the last decade. We focus on features of what urban planners call vibrancy: measures of positive, healthy activity or energy in an area. Historically, vibrancy has been very challenging to measure empirically. We explore the association between safety (violent and non-violent crime) and features of local neighborhood vibrancy such as population, economic measures and land use zoning. Despite rhetoric about the negative effects of population density in the 1960s and 70s, we find very little association between crime and population density. Measures based on land use zoning are not an adequate description of local vibrancy and so we construct a database and set of measures of business activity in each neighborhood. We employ several matching analyses within census block groups to explore the relationship between neighborhood vibrancy and safety at a higher resolution. We fi nd that neighborhoods with more vacancy have higher crime but within neighborhoods, crimes tend not to be located near vacant properties. We also find that more crimes occur near business locations but businesses that are active (open) for longer periods are associated with fewer crimes.

This is particularly fascinating to me because I live my life in the middle of this particular data set and am part of it. So it is very interesting to compare what the data seem to be saying with my own experiences and impressions.

The lack of correlation between population density and crime is not surprising. Two neighborhoods with identical density can be drastically different. The correlation between poverty and crime is not surprising – people who are not succeeding in the formal economy and who are not mobile turn to the informal economy, in other words drug dealing, loan sharking and other illegal ways of trying to earn an income. If they are successful at earning an income, they tend to have a lot of cash around, and other people who know about the cash will take advantage of them, knowing they will not go to the police. Other than going to the police, the remaining options are to be taken advantage of repeatedly, or to retaliate. This is how violence escalates, I believe, and it goes hand in hand with development of a culture that tolerates and even celebrates violence, in a never-ending feedback loop.

The puzzling part comes when they try to drill down and look at explanatory factors at a very fine spatial scale. They found a correlation between crime and mixed use zoning, which appears to contradict the idea that eyes on the street around the clock will help to deter crime. And they found more crime around businesses like cafes, restaurants, bars and retail shops. They found that longer open hours seemed to have some deterrent effect on crime relative to shorter open hours.

I think they have made an excellent effort to do this, and I am not sure it can be done a lot better, but I will point out one idea I have. They talk about some limitations and nuances of their data, but one they do not mention is the idea that they are looking at reported crimes, most likely police reports or 911 calls. It could be that business owners, staff and patrons are much more likely to call 911 and report a crime than are residential neighbors. The business staff and patrons may see this as being in the economic interest, increasing the safety of their families, and the (alleged) criminals they are reporting are generally strangers. In quieter all-residential neighborhoods, people may not observe as many of the crimes that do occur (fewer “eyes on the street”), they may prefer not to report crimes either through a sense of loyalty to one’s neighbors, minding one’s own business, quid pro quo, or in some cases a fear of retaliation. There is also the factor of some demographic groups trusting the police more than others, although the authors’ statistical attempts to control for demographics may tend to factor this out.

 

Richard Berk

1 Reply

Here’s a Bloomberg article on Richard Berk, a statistician at the University of Pennsylvania whose algorithms are used for parole, probation, and sentencing decisions.

Risk scores, generated by algorithms, are an increasingly common factor in sentencing. Computers crunch data—arrests, type of crime committed, and demographic information—and a risk rating is generated. The idea is to create a guide that’s less likely to be subject to unconscious biases, the mood of a judge, or other human shortcomings. Similar tools are used to decide which blocks police officers should patrol, where to put inmates in prison, and who to let out on parole. Supporters of these tools claim they’ll help solve historical inequities, but their critics say they have the potential to aggravate them, by hiding old prejudices under the veneer of computerized precision. Some people see them as a sterilized version of what brought protesters into the streets at Black Lives Matter rallies…