A Time to Be Born

October 19, 2012
Posted by Jay Livingston

Muhammad Ali and Evander Holyfield, Ty Pennington and Chris Kattan, John Le Carre and Trey Parker. Give up? They all were born on October 19. Happy Birthday.

The birthday problem came up again on a New York Times blog earlier this month.

How many people do you need in a room to get 50-50 odds that at least two of them share a birthday?

The official answer is 23.  The blogger, Steven Strogatz, takes you through the math (without once using the word factorial!) and even embeds the video clip of Johnny Carson getting it wrong. 

But even 23 is too high.  It assumes that birthdays are randomly distributed throughout the year.  But they’re not.

(The lack of a zero-point exaggerates the differences.  Still, September babies outnumber January babies by nearly 10%.)

The first thing it called to mind was the hockey aperçu made by Paula Barnsley but made famous by Malcolm Gladwell in the first chapter of Outliers.  The revelation takes place at a junior championship hockey game in Canada.  One of the spectators was Canadian psychologist Roger Barnsley.

   He was there with his wife, Paula, and their two boys, and his wife was reading the program, when she ran across a roster [that listed the players’ vital statistics]
   “Roger,” she said, “do you know when these young men were born?”
Barnsley said yes. “They're all between sixteen and twenty, so they'd be born in the late sixties.”
   “No, no,” Paula went on. “What month.”
   “I thought she was crazy,” Barnsley remembers. “But I looked through it, and what she was saying just jumped out at me. For some reason, there were an incredible number
of January, February, and March birth dates.”

In Canadian age-graded sports, kids are grouped by the year of their birth.  A boy born on Jan. 1, 2000 and a boy born on Dec. 31, 2000 are both twelve years old, at least for purposes of hockey eligibility, even though one is a year older than the other.  The older 12-year old is likely to be bigger and to have whatever other physical advantages develop with age.

Horse racing uses the same rule. Officially, every thoroughbred has the same birthday – January 1.  So the breeding season peaks in the late spring.  Most Kentucky Derby winners are foaled in March, very few after May. 

Is anything similar going on among human breeders, usually called parents?  Apparently not. The numbers for the early months are low rather than high.  (In Canada too, births in the first quarter are lower than in the next seven months.) 

Some school systems use a cutoff date of September 1, so all those September babies have an edge, but if parents were breeding rationally, we’d expect lots of births in the following months as well rather than the dropoff shown in the graph.

It looks as though most parents are not breeding rationally, or if they are, other considerations are affecting their scheduling. 

Yes, you can find articles (this one, for example) about competitive parents redshirting their 5-year olds – delaying a child’s entry into kindergarten for a year so the little tyke will have an edge over his even littler classmates.  It would appear that there are too few of these to make a blip in the graph. Still, I wonder what the graph would look like if it were based only on upper middle-class births. 

In any case, births are not distributed randomly. Cue The Byrds, channeling Pete Seeger channeling Ecclesiastes: “To everything there is a season . . .  a time to be born . . ..”

Unwed Moms or The Hood

October 17, 2012
Posted by Jay Livingston

The question to Obama was:

In 2008, you stated you wanted to keep AK-47s out of the hands of criminals. What has your administration done or planned to do to limit the availability of assault weapons?

Obama did actually respond to the question, in part. 

I also share your belief that weapons that were designed for soldiers in war theaters don’t belong on our streets.

And he even offered a relevant fact:

in my home town of Chicago, there’s an awful lot of violence and they’re not using AK-47s. They’re using cheap hand guns.

And then he wandered off into schools and opportunity.*

CROWLEY: Governor Romney, the question is about assault weapons, AK-47s.

Romney ignored the moderator ad made no mention of AK-47s.  He merely said he wanted no new gun laws. Then he too quickly skipped to matters that have nothing to do with the availability of AK-47s: education, hope, opportunity, and . . .

let me mention another thing. And that is parents. We need moms and dads, helping to raise kids.  . . . But gosh to tell our kids that before they have babies, they ought to think about getting married to someone, that’s a great idea.

Or as someone said or tweeted:

Guns don’t kill people. Unwed mothers kill people.

With variables like unemployment and single-parent families, it’s crucial to distinguish between individual effects and neighborhood effects.  Romney is thinking only about individual effects  – the effect of the family on the child.  The assumption behind Romney’s statement is that single parenting is bad parenting, and therefore it will have bad consequences.**

I confess that I haven’t kept up with the literature on crime, but as I recall, the individual-level correlations are not all that strong.  When you control for other variables, children of single parents or children of unemployed parents are not much more likely to commit violent crimes. 

So the problem is not the unwed mother or the unemployed parent.  The problem is what happens to a neighborhood with high rates of single-parent families and high rates of unemployment. 

We know this intuitively.  Imagine two boys – one with a two-parent family, the other with a single mother.  The two-parent kid lives in a neighborhood where most families are headed by single mothers and there are few employed men.  The single-mother boy lives in a neighborhood where most families have two parents, and most men have jobs.  Who is more likely to commit a violent crime? 

Or imagine that you yourself have a kid and a spouse.  If family structure is the overriding factor, and you wanted to be sure your kid didn’t commit violent crimes, then you would have no preference between those two neighborhoods.  But would you?

Back in the 1980s, researchers like Rob Sampson were shifting the focus from individuals and families to neighborhoods.   Unfortunately, political debates about crime and violence often ignore what every parent knows: that  parents can do only so much, and kids are subject to many influences outside the home.***

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* When I become czar of presidential debates, we will have not just time-keepers to make sure speakers stay within their time but topic-keepers to remind candidates when they are not addressing the question that was asked.  In the three debates this month, topic-keepers would have been very, very busy.

** Romney hedges – “A lot of great single moms, single dads” – but it’s clear that he thinks these are lucky exceptions to the general rule.

*** Philip Cohen has conceptual blog post about the link between unwed mothers and violence (here).

Dialing for Donations . . . and Deductions

October 16, 2012
Posted by Jay Livingston

Google finishes your sentences for you. At least, they finish your partially typed search string, based on what searchers before you have sought. 

Then Google gives you a list of Websites based on their Algorithm. The way people talk about The Algorithm, I get a picture of some powerful, mysterious god.  Those who can unravel its secrets stand to gain mightily by having their Website win the race to the top. 

Maybe the Republicans have nailed it. Or maybe they just paid for it.   Here’s what you get if you want to donate money to the Democratic National Committee.  (Pink-background sites are paid ads.)

I guess the GOP thinks they’ll get some money by advertising to people who want to give to the Dems.

A search for donating to the Republicans has no Democratic ads. 

(Click on the image for a larger and possibly clearer view.)

What’s interesting here is the autocomplete.  Apparently, a lot of people who want to donate to the Republicans are also concerned that they get a tax break for their largesse.  Which  pretty much confirms what they’ve been telling us about their position on taxes all along – paying less on their taxes is really, really important to them.

Do Pro Athletes Want Gambling?

October 14, 2012
Posted by Jay Livingston

The obits for Alex Karras  all noted that the NFL suspended him and Lions teammate Paul Hornung for gambling.  Then there’s Pete Rose, whose gambling has kept him out of the Hall of Fame.  And Tim Donaghy, the NBA ref who later said his gambling affected the way he called games. 

What’s up with White sports dudes and gambling? 

Chad Millman at ESPN touts the latest issue of their  magazine (he’s the editor) with the promise of some data.

In that issue we run one of our Confidential polls, in which we question dozens of athletes about taboo topics. In the current version we asked 67 jocks from the four major sports: . . . do you think sports betting should be legalized?

Let’s stipulate that a non-random sample of 67 jocks-we-could-get-to-answer-our-phone-call divided into four categories is less methodologically rigorous than we would prefer.  Still the differences among the sports are striking.  The NHL players were overwhelmingly in favor of legalized sports betting, the NBA players against it.

Here’s a graph that makes the ESPN data look more impressive than it actually is.

The Whiter the sport, the more its professional practitioners want legalized gambling.

Millman is not an academic, so he didn’t end his article with a call for further research (and funding).  But maybe he should have.