Is There An Actuary in the House?
Special note to our readers - bear with us in this post. We know crunching numbers is boring, but we're really wondering about this stuff.
More crime reduction?
More crime reduction?
- Overall crime was down for the 29th consecutive month in Chicago, according to preliminary monthly crime statistics for the month of May released by police Sunday.
Total crime in the city fell 5.9 percent compared to crime numbers through May 2010, police said in a press release.
One of the more prevalent drops in May is that of homicide, down 16.3 percent. Through the end of May, there were 27 fewer homicides this year than the same timeframe in 2010, police said. More than half of the 25 police districts citywide reported decreases in their homicide numbers.
Twenty-nine consecutive months of falling crime. Twenty-nine. Almost two-and-a-half years. We've joked here a few times about how "if crime keeps falling, we're going to owe a bunch to the future." Now we're starting to wonder.
As you see from the quoted article, the Department says crime fell "5.9 percent compared to crime numbers through May 2010." No note if that's year-to-date or what, but it makes us wonder. Every number we can recall over the past two years has been in that area, give or take a bit. So let's try a little experiment.
Let's say that twenty-nine months ago, there were 100 crimes in Chicago. Now let's say, for the sake of making things simple, that every month there was a 3% drop in crime. We're attempting to err on the low side because we really don't recall any drops of under 4% (we might be completely off base). And to be statistically honest, we'll apply that 3% to each month's new number of crimes (there are ways to manipulate statistics, but we'll avoid that.) We'll round the numbers in accordance with accepted mathematical processes:
As you see from the quoted article, the Department says crime fell "5.9 percent compared to crime numbers through May 2010." No note if that's year-to-date or what, but it makes us wonder. Every number we can recall over the past two years has been in that area, give or take a bit. So let's try a little experiment.
Let's say that twenty-nine months ago, there were 100 crimes in Chicago. Now let's say, for the sake of making things simple, that every month there was a 3% drop in crime. We're attempting to err on the low side because we really don't recall any drops of under 4% (we might be completely off base). And to be statistically honest, we'll apply that 3% to each month's new number of crimes (there are ways to manipulate statistics, but we'll avoid that.) We'll round the numbers in accordance with accepted mathematical processes:
- Month #1 - 100 crimes;
- Month #2 - 100 crimes x .03 = 3......97 crimes occurred;
- Month #3 - 97 crimes x .03 = 2.91......94 crimes occurred;
- Month #4 - 94 crimes x .03 = 2.8......91 crimes occurred;
Now carry that out twenty-nine times. Make a spreadsheet. Use paper, pencil and a calculator. What you get is by Month #29, forty-one crimes have occurred. From one hundred all the way down to forty-one. That's a 59% drop in crime in just under two-and-a-half years.
Does that even seem possible? It doesn't feel possible, but our perceptions, like everyone else's, are colored by media coverage and first-hand viewing of conditions on the ground. We've got way more than 2.5 years on the job and we just don't see it being 59% safer than it was in 2009. We'll admit that we don't have the exact percentages the Department is using to come up with these numbers, but we also don't think we're very far off.
Any geniuses out there?
Does that even seem possible? It doesn't feel possible, but our perceptions, like everyone else's, are colored by media coverage and first-hand viewing of conditions on the ground. We've got way more than 2.5 years on the job and we just don't see it being 59% safer than it was in 2009. We'll admit that we don't have the exact percentages the Department is using to come up with these numbers, but we also don't think we're very far off.
Any geniuses out there?
Labels: stats
posted by SCC at 12:03 AM
50 Comments:
Lies, Damn Lies and Statistics.
Crime is Down.
I got a bridge for sale, anyone interested?
Bullshit.They Reclass Crimes.burgary=criminal damage.strong arm robbery = battery.hommicide= Death Investigation.
I think, and I know it's a dangerous thing to do, that what the stats are referring to is a decline in crime for 29 straight months comparing those months to the same month in the prior year.
I could very well be wrong.
Figures lie...
Look at all the people shot by police lately. Does this give you a safe feeling?
How about the loss of five officers last year? Are you feeling safer now?
In the past couple of weeks of semi-warm weather, there has been numerous murders and shootings. Feeling any safety in that?
I know that there is a lot of tomfoolery going on with UCR coding.
A lot of 0110's are coded as 5084.
Meanwhile our autistic bosses keep counting and counting...snow tows, curfews, ANOVS, movers, contact cards...
...and liars figure.
Do I get another ribbon?
After being victimized 3, 4, or 5 times people just stop reporting real crime. They figure it doesn't do any good. Except for homicide the number will reflect that. Just reading the stories about all the crime going on around the city it sure doesn't seem any safer to me.
The only geniuses are the press and the goofs who figure this stuff out. Let's use the number 100. In 2009 20 people out of 100 were murdered. That would be 20%
Now in 2001 only 10 people out of 100 were murdered. Would you say that ia a 10% drop in homicides? Or would you say it is a 10% drop in all crimes because those 10 people are not around to do any crimes?
Don't look now but all that 'missing' crime is stuck in AIRA somewhere.
It s just reported crime is down. Try using call-back to make a report. They never answer and give you a recorded message stating they'll call you back in a few hours to make the report. Even if you go to the station, you'll get rude treatment.
I don't think your calculations are correct. Unfortunately, I just barely got through statistics, but I will pull out my books and see if I can figure it out. Something doesn't look right with them--any statistics buffs out there?
As the noted and famous author and American once said: There are lies, damn lies, and statistics
Sorry, the author was Mark Twain
Regardless of what the numbers say, it appears that the crime is moving out of the usual crappy neighborhoods and infesting areas in the past relatively untouched by the scourge.
I believe the comparison is being made between January through May 2011 and January through May 2010. I suspect that the declining crime numbers come from comparing a month with the same month a year earlier. Even if it is a comparison with the previous month, the "decline" could be as little as 0.1% which would be essentially flat (1,000 arrests vs 999). After 27 months the difference might be 950 compared with 1000, a 5% decline.
As one who is out there everyday, I can say for certainty that I feel less safe now than anytime in my 20 years.
say what????????????????????????????????????????????????????????????????????????????????????????????????????
I haven't seen the actual numbers, but my best guess is they used what is called statistical baseline calculations. So you start with a baseline of 100; then each quarter from using the 100 as the baseline gives you your percentage. So each quarter is defined by the original 100. What you have described is called trend analysis, and I am certain they didn't use that, well because it would be honest. I'll try and get the numbers and do an actual analysis and get back to you fine people.
Stay safe all officers reading this, understand there is a silent majority who still supports you !
I think your calculations are based on an erroneous assumption. You show a progressive reduction, with each month reducing the numbers from the month before. The percentage reduction figure is calculated from the previous YEAR, not the previous MONTH. So, if you have 12 months of 4% reduction as compared to the same month of the previous year, you end up with roughly a 4 percent reduction in the figures for the YEAR. Common sense will validate this approach - you know that there are natural variations in the rate of any human activity- month to month, seasonal, day versus night. If activity goes up or down in a given month, you may see a noticeable change in the activity month to month, but the cumulative effect may be slight.
Example: You will have seasonal variations in bicycle use on the lakefront, which are apparent when comparing February and March, but the real test is the change between March 2010 and March 2011. Same method used in the business reports comparing retail sales figures.
RE: Crime reduction 'stats;
KOOL-AID, KOOL-AID, TASTE GREAT, WISH I HAD SOME, CAN'T WAIT....Please, may I have another?
As a young tough, runnin, gunnin and part 1in, I met some detectives.
Instead of the usual, "Ya got nuthin kid", they stated,"No crime until overtime."
What a fun game we USED to play!
Stay alert, stay alive. Always remember, let's do it them before they do it to us.
It's a great way to justify further reducing the number of P.O.s in the budget. Confuse everyone with bullsh*t statistics and save big $$$ come contract negotiation time.
And when I was with the NYPD, I remember...
Lairs figure and
Figures lie
FUNNY numbers of auto thefts and arson are up. hmmm maybe because you can't mess with crime that is documented by insurance companies.
I think your calculations are based on an erroneous premise - the percentage reduction figures are based on comparison with the same month in the previous year. Your calculation is based as if the reductions were from the previous month figures. The aggregate figure for comparison is the total decrease for the preceding year.
To use your example of a 3% reduction each month, with a base of 100 incidents each month, the calculation would look like this:
Month #1 - 00 crimes x .03 = 3......97 crimes occurred;
Month #2 - 100 crimes x .03 = 3......97 crimes occurred;
Month #3 - 100 crimes x .03 = 3......97 crimes occurred;
Month #4 - 100 crimes x .03 = 3......97 crimes occurred; (and so on....)
This would result in a 3% reduction for the year. You can look at this in a common sense way, as well. Bicycle riding on the lakefront would be a good example showing variance from month to month, as well as comparing the same month year to year. You would see a big variance between January and May, with the numbers increasing each month. This, by itself is meaningless, except as it reflects seasonal changes. Where the changes become meaningful is when you compare the same month year to year. Each month is compared to the same month in the previous year. This is the same methodology used by business when calculating differences in retail sales, factory production, etc.
What you have to watch for is the use of statistics in "mixed" form: If I quote the monthly statistics compared to the same month last year, it will show a valid change, When I quote the "drastic increase" in bicycle use from March to April, it just shows a blip.
I have to recommend the little book "How to Lie with Statistics" by Darrell Huff, which is available on Amazon. (You have to know HOW to cheat before you can catch the cheaters.) BTW, I'm not an actuary, but I have taught research and statistics at the college level.
During the Vietnam War years the Pentagon issued regular and over optimistic body counts of enemy dead.
At some point an anti-war group that was keeping count totaled it up and realized that the entire population of Vietnam was reported to have been killed so the war must be over due to everyone being dead.
Perhaps something similar will occur here, crime will keep going down until it doesn't exist. Except for those dozens of Englewood, Chatham and West Side residents killed each weekend.
Then what?
They're full of shit and fucking with numbers as usual. Crime isn't down in this shit hole city, it's way up. The way things are it's going to keep going up. I guess the powers that be think that if they just keep telling the lie that crime is down, that it will eventually become the truth. Or maybe they think that if they bullshit enough citizens long enough that they'll start to believe their bullshit.
I was reading the Wilmette-Kenilworth weekly rag recently and there were a couple of burglaries and assorted minor crap in Wilmette for the week but there were NO reported crimes in Kenilworth. None. Not any. For the whole week!
Now the per capita income in Kenilworth is over $100,000 and the median income is over $200,000. And the population demographics is reported at 0.16% black. The 4 black people living there must be well behaved and have a pretty good income. They aren't all domesticating and flash mobbing and shit.
Wait till Jesse Jackson and Father Pfleger find out about Kenilworth. They will want some of dat nice housing for Section 8. Maybe they will march and picket and boycott and we can be treated to another Pfleger style rant.
These statistics are given out by the same people who report one million or two million or three million people attending the Air & Water show and similar events. The report is issued in time for the evening news.
Actually, there is a guy named Louie who takes the call and yells, "hey, Tommie, how many we get today? A mil and a half sound OK?" and Tomie replies, "Naw, we used that last time, this has to be bigger 'cause the boss wants more than last year, better make it two Mil" And Louie tells the news media that through scientific calculations that two million people attended.
And people read that crap and believe it.
Here is a good rule of thumb: If the City of Chicago reports figures, money, statistics etc. it is a damn good bet that it is all bullshit.
Want better numbers? Use a Ouija board.
hey some officers 19-p every call
make an assault , simple battery on every domestic dist , teens fighting , find a victim , make a battery case report , victim declines to sign complaint or advise warrant , shots fired look for a shell casing , make report and do an inventory
Sorry SCC I have to disagree with you on this. You see the department's numbers are correct.
The math clearly shows we have a NEGATIVE number of crimes committed each month.
In 29 more months we should be around negative 100 crimes per day
Yeah pretty funny to believe that crime is down.
What do they define as crime?
It is not spelled out and the reader is left to assume what crime is. Crime to them may just not include what you think it does.
Look at the question of residency with the mayors race.
Many people thought they knew what residency meant, they though we were talking about the commonly accepted definition and it turns out the political apparatus has a totally different meaning that suits their needs.
Yeah, crime.
Being an illegal immigrant is a crime. An illegal immigrant with a phony social is a crime. Driving while talking on your cell phone is a crime. However we call it something else and turn the other way.
How about all the white collar crime from the housing mortgage frauds? Not one banker in cuffs for the robo-signing frauds on the courts for submitting fraudulent affidavits.
And these crimes that are counted.
Even the FBI will not used the Chicago numbers as they know they're counted differently than any other city.
The numbers are b.s.
If a homicide gets pleaded down to manslaughter or an act of self defense -- or if the witnesses are intimidated to not show up and the case is dropped, turned back into a death investigation, how is that crime counted?
27 fewer murders they say.
Well we had a pretty cold April, and May from last year. Don't worry we'll catch up.
These politicians and their puppet leaders are quick to claim credit for more coppers on the street as being the reason crime is down.
But if it actually is how about the Dec 2009 suspension of the MGT push program being at least partly responsible? We know that 70% of the violent crime is repeat offenders! They'll be back on the streets soon. If crime is dropping so much why are the states prisons stilled filled to the rafters with people!
That said, judges knowing that the prisons are full are more likely to cut some slack to many criminals. Reducing the charges to crimes and place them on probation instead right?
How many open death investigations are there? There's some more crimes not being counted I'll bet.
You know the old saying " The figures don't lie and the liars can figure.
Nevertheless, the way the numbers are manipulated and presented we are left to make a lot of assumptions.
The cities population itself has been going down. What's the crime rate per every 100,000 people compared to like cities?
When we say: "Overall crime was down for the 29th consecutive month in Chicago" are we saying cumulatively on a month over month basis?
I know that's what is being implied but maybe we are assuming too much.
For example if we find a month were crime hit a peak at let's say 100 and use that as the base of our comparison...and we keep comparing crime to that peak we could have 80 crimes the next month and then 90 crimes after that and still say that crime is down for those two consecutive months (compared to the peak) even though on a month to month basis the crime has gone up from 80 to 90.
Not to mention if the definition of what overall crime has changed over that period. Like an illegal immigrant has become an undocumented alien, a battery could be now called a domestic disturbance and maybe those are no longer considered a crime.
Nevertheless crime falling for 29 straight months could mean a fall as little as 29 because all it takes is a drop of one...one dropped case, one lost paperwork, one UCR code change. Just one less than the prior month and you're done.
Hey, the city is so safe now tell the ex mayor and the alderman and the rest of the politicians to give up their security details they don't need them anymore. Crime no longer exist!
It's not surprising how these numbers are obtain.
United Road Towing's agent called Go-Go Towing stole my legally parked and license vehicle from right in front of my home where I've been parking it for the last five years.
Called the district even talked to a supervisor and couldn't even get a report filed.
When I recovered the vehicle from the city pound it was extensively damaged and I ask for a police report on that too and was told no -- the officers refused to help me.
The city that works is bullshit.
It ain't working for me that's for sure.
I have a PhD in statistics...and I can assure you that there are numerous ways to distort percentages (which likely is not a news flash to anyone here). That said...if I took the time (and am willing to do so upon request) I could likely figure out what they are doing and where these statements about the numbers are coming from. When I get home from work, I'll take a look at the article in greater depth and see if I can't spin a story of my own from these numbers.
An additional note: Just b/c I'm a PhD doesn't mean i'm a liberal jerk or that my head is in the clouds on things here. I am a FOID carrying, gun owning libertarian who studies math and reading education. It's likely the only thing as depressing as the crime in this city...the education system here (actually the parents, but I digress.)
Either way...i'll look into this and further bulletins as events warrant...as it were.
I know stats.
The press release is confusing, but I think your third "Anonymous" has the right idea. Here is what the press release says:
"This month's results mark the 29th consecutive month of crime drops overall and in violent and property index offenses in the City. The Department reported that total crime was down 5.9 percent compared to crime numbers through May of 2010. Violent crime in the city decreased 10.2 percent while property crime was down 4.8 percent"
So I think the key is that they (meaning CPD HQ) is talking about crime "compared to crime number through May 2010." I suspect then, that when they say we are in the 29th consecutive month of drops, they are talking about drops compared to crime from over a year ago. So for example, 29 months ago it was January 2009 and when they reported crime dropping back then they were reporting a drop compared to January of 2008.
By the way, I love the blog and will try and follow you more closely now that I have my own blog up and running. One of my favorite subjects is crime and public policy -- I'm generally sympathetic to a lot of what you say except that I think benefits have to be cut for all government workers, including cops.
I say that even though I'm a government worker and my cousin is a cop (in Austin) and is getting married this month so if you know him give him my best -- he's a good guy.
I think you should update this post with Jim's comment as the baseline. I think he explained (a) how they can say this, and (b) how relatively meaningless it is.
I say that even though I'm a government worker and my cousin is a cop (in Austin) and is getting married this month so if you know him give him my best -- he's a good guy.
6/06/2011 02:45:00 PM
when you see him at the reception, be prepared for his reaction to your generous offer to support cutting his income.
"Fun & Fuckery With Numbers"
By RMD
j-fled
9.5
McFibber
&
Dr. Muthafuckin' Seuss
Yeah... We'll run right out and buy this one.
We'll have the entire "Municipal Mookery" collection...
"My Foot... Your Ass!"
"Only Suckers Play By The Rules"
"Paddy Daley Sez Hooray For Me & Fuck You"
"Cut Their Pay and Steal Their Pension"
"That Cat Just Took A Shit In Your Hat"
Jayzus...
What THE ENTIRE UNIVERSAL FUCK do these fools hope to accomplish with these gyrating, oscillating & rotating numbers?
The variable is bullshit...
The constant is bullshit...
What the fuck do you think the product is going to be?
Stats aren't our cup of tea but dammit, we can see what's going on and we can count higher than ten without sitting on the floor and taking our shoes off to count toes for assistance...
When will people stop buying the 100 proof crazy that the city is selling? Isn't the kool-aid enough??
Whoever owns, compiles & authors this shit needs a pocket kicked in their ass...
Chalkie on his way home from Paul and Joes made a stop in 16 today. Chalkie do you ever sleep ?
Don't look now but all that 'missing' crime is stuck in AIRA somewhere.
6/06/2011 06:34:00 AM
lmao
Interesting phenomena going on in juvenile court the last few weeks. Dramatic increase in cases referred to court , many more juveniles put on probation, states attorneys seem to be toughening up filing more cases and pushing them thru. More work for us , but if it will make more of them realize they're not being played with anymore, I'm all for it.Several judges are also locking up juveniles left and right.Problem will still be with the too many , too easy judges who won't make them accountable , but it seems like some headway has been made.Maybe things will turn for you guys soon too .
Although the Feds are totally corrupt- does the FBI even accept crime statistics from chicago? No- when they have headlines on the news media about US crime-- chicago is never mentioned. Even the corrupt Feds do not believe the statistics.
Feds corrupt? Let us start with pulling the Blago wire down before whomever had a chance to talk to Blago. The monitors know who he is-- and I bet if they keep their mouths shut- promotions all the way.
Whitey Bulger
John Connelly -- fbi asac who is serving prison time in florida for accessory to murder- others that are too numerous ( and coveredup ) to mention
it is all legit folks
Math gives me a headache. Since 3rd grade where I lost my way, I've struggled. I know people will say stats isn't math--I call bullshit. And screw you Sister Paulette, if you're still alive!
I have a PhD in statistics...and I can assure you that there are numerous ways to distort percentages (which likely is not a news flash to anyone here). That said...if I took the time (and am willing to do so upon request) I could likely figure out what they are doing and where these statements about the numbers are coming from. When I get home from work, I'll take a look at the article in greater depth and see if I can't spin a story of my own from these numbers.
An additional note: Just b/c I'm a PhD doesn't mean i'm a liberal jerk or that my head is in the clouds on things here. I am a FOID carrying, gun owning libertarian who studies math and reading education. It's likely the only thing as depressing as the crime in this city...the education system here (actually the parents, but I digress.)
Either way...i'll look into this and further bulletins as events warrant...as it were.
6/06/2011 02:03:00 PM
Ok stats guy, I'm asking. Please help us expose the city's bullshit so that they can't deny the truth. Sort of like Cong. Weiner. Isn't that funny that's his name???
And BTW, the stats portion of one of my MBA classes starts in about two weeks.......
And screw you Sister Paulette, if you're still alive!
6/06/2011 08:40:00 PM
i remember you, you little sweet thing.
always asking for the ruler.
It's not surprising how these numbers are obtain.
United Road Towing's agent called Go-Go Towing stole my legally parked and license vehicle from right in front of my home where I've been parking it for the last five years.
Called the district even talked to a supervisor and couldn't even get a report filed.
When I recovered the vehicle from the city pound it was extensively damaged and I ask for a police report on that too and was told no -- the officers refused to help me.
The city that works is bullshit.
It ain't working for me that's for sure.
6/06/2011 12:47:00 PM
File a Mayor's Complaint. Yes, there is such a thing.
It's the 'consecutive' that appears to throw you off.
What the statistics say is that for the last 29 consecutive months, each month's crime rate was X% less than the same month the prior year.
To use your example. Say January 2010 had 100 crimes, so, a 5% reduction means that January 2011 had 95 crimes. Next, say February 2010 had 100, then Feb 2011 had 94 if crime fell by 6%.
This happened for 29 consecutive months. On aggregate, your mistake is compounding the reductions, when really it's a weighted average of all the months.
So, a number of say 10% over the last cumulative 29 months would make more sense if each month's rate compared to that month's in the prior year was reduced around 10%.
The answer is simple. Send all stats to NASA to calculate. After the last shuttle launch next month they won't be too busy.
Ok stats guy, I'm asking. Please help us expose the city's bullshit so that they can't deny the truth. Sort of like Cong. Weiner. Isn't that funny that's his name???
And BTW, the stats portion of one of my MBA classes starts in about two weeks.......
First, I'm a stats lady. Second, I'd be glad to look at it. My first guess is that they are misrepresenting the nature of the statistics. Specifically, not taking into account the effect of neighborhoods, SES, etc. It is quite simple to manipulate the percentages if you don't explain how they are conditioned. It shouldn't be too hard to figure out. I'll report back.
WRT your MBA stats class. It'll be fine, but I also tutor to pay off student loans...just a thought.
This happened for 29 consecutive months. On aggregate, your mistake is compounding the reductions, when really it's a weighted average of all the months.
So, a number of say 10% over the last cumulative 29 months would make more sense if each month's rate compared to that month's in the prior year was reduced around 10%.
6/06/2011 11:18:00 PM
the devil is always in the details, thus, selected details are manipulated and presented as whole and complete truth, producing deception, aka lies.
the goal is to always be able to claim that today is better then yesterday, and to always take credit for the claimed improvement.
what the professional bullshitters count on is the majority of their target audience having short memories.
one of the politicians' many credos:
you don't have to fool some of the people all of the time, nor do you have to fool all of the people some of the time, nor do you have to fool all of the people all of the time.
you only have to fool just enough of the people at just the right time.
once elected, you can pretty much do what you want.
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