Monday, April 28, 2008

FLDS and arithmetic


I believe that when I read the original CNN report, it included the fact that two of the girls were actually pregnant. But either I misread it or the story has been revised since--at this point there is no number for pregnant girls, only for the number claimed to be either pregnant or mothers. We'll have to wait and see which is the case. It's a bit odd that they would simply lump the numbers together.

It appears, incidentally, that whether the girls actually are 17 or under is unclear. The Texas authorities seem to be judging age by appearance and refusing to accept birth certificates as evidence, at least according to a news story. Another news story refers to CPS documents claiming three pregnant girls, with at least one of them disputed by an attorney for the FLDS

Further update, uncorrection

The Time magazine story online gives the figure of only two girls pregnant. One might almost suppose that someone in the Texas CPS realized how bad the figure was for their argument and changed the account they gave to CNN.

According to the most recent statement of the Texas authorities, as reported by CNN:

1. 53 girls between 14 and 17 are in custody.

2. 31 of them either have had children or are pregnant

3. 2 are pregnant.

Assuming CNN is accurately reporting the figures, two points are worth noting.

First, the two figures appear inconsistent. If, on average, two girls are pregnant at any one time, they should be producing about ten children in four years--but the authorities claim at least 29 children–more if some of the girls have had more than one child. Even allowing for random variation in the rate of pregnancies, a factor of three is an awfully big discrepency.

[On further consideration this is wrong. At the end of four years, ten children will have been produced by mothers who were 14-17 when the children were born, but only half of those mothers will still be under 18, so only about five children will have been produced by mothers who are still in the 14-17 range. According to the Texas authorities at least 29 were.]

Perhaps I'm unduly suspicious, but it occurs to me that it's easier to prove the state is lying about whether a girl is pregnant than about whether she has had a child. To what extent the latter can be disproved with DNA evidence I don't know–I gather the population is pretty inbred, which may make that harder. The girls are all under state control–it will be interesting to see if doctors selected by the parents are permitted to examine them for evidence that they have or have not had children.

Second, a little googling turned up a teen pregnancy rate in Texas, for girls 15-17, of about 4%. [another source has about 6%] So the number of pregnant teens actually present in the FLDS population is about average. Oddly enough, that wasn't the CNN headline.

I also note that CNN is still saying, of the initial caller, that "That girl has not been found and authorities are investigating whether the call was a hoax." They neglect to mention in the story that the identity of the hoaxer has been pretty clearly established, as reported in the London Times a week or so ago. The link that supposedly goes to a video on "who might be behind the calls" actually goes to a video about minors having children, with an outraged woman reporter initially confusing the number who have had children (supposedly 25 in her report) with the number who are pregnant (2). There is a link in small print in the "Don't Miss" sidebar which takes you to a reasonably complete account of the story, but one that scatters the bits of evidence through the piece and never actually comes out and reaches the obvious conclusion.


Anonymous said...

It could be that the 16 and 17 year olds represent the 29 girls who were pregnant, and the 2 that are now pregnant are 14 or 15. That's at least consistent with the reported data; we'd need to know more about the distribution of ages to merit suspicion.

David Friedman said...

I don't think rkn's conjecture works out mathematically. Assuming a uniform age distribution, the two pregnant ones would be two out of about 26. With that pregnancy rate, and girls not getting pregnant at 16 or 17, you don't end up with anything close to 29 children.

montestruc said...

The state is I suspect skewing the results by arguing that any young woman who is pregnant or has young children and might plausibly be under 18 or under 18 at the time of the pregnancy are lying about their ages, even when they produce birth certificates.


One attorney demanded to know why CPS won't believe an 18-year-old mother who has a certified birth certificate showing she is 18 and yet remains in state custody.
----end quote----

Anonymous said...

Assuming a uniform age distribution ...

Which I didn't - and that was my point. What information in the news report merits that assumption?

Elizabeth A said...

Pregnancy rates are usually statements of the number of pregnancies per thousand women over a period of time - not how many women (or how many teenagers) are pregnant today, but how many over the course of a year.

It's misleading to assign this group a pregnancy rate based on the number who are gestating today, compare that number with the population rate (stated as pregnancies per thousand per year) and draw any kind of conclusion. I'm really surprised to see such transparent misuse of statistics.

Anonymous said...

Oh my god---pregnant seventeen year olds!! And 16 and 15!!! Not to mention that Texas lies. Temple sex bed? Lies. Cyanide documents, a la Jim Jones? lies.

I thought the Texas authorites said these people raped children. Where are the stats on 13 and younger? Isn't that what led to the raid?

If they took the kids away from every member of a type of group which has pregnant young ladies aged 17, would catholics be allowed to have kids? How about blacks? I know whites have pregnant teenagers. How about the Joooooooz. I know they have pregnant teenagers. Let's take away the kids of the Jooooooooooz.

David Friedman said...

Elizabeth is puzzled by my use of statistics. I don't see the problem.

Since pregnancy usually takes about nine months, it's straightforward to deduce the rate of children produced per year (provided the pregnancies result in one offspring each)from the number pregnant at one time. If some of the pregnancies end with abortions or miscarriages, the ratio of children to pregnancies will be lower, making the claimed figures even less plausible.

If, on average, at any given time two women in the age group are pregnant, then the group as a whole is producing two children every nine months. Multiply that by 48 months (four years) and you get the number that would have been produced by the whole four year age group.

So to make the claimed figures work, you have to assume that, for some reason, the number of girls currently pregnant is a third of its average value over the past four years.

What part of that can't you follow or seems mistaken to you?

Anonymous said...

The community is made up of immigrants. Not everybody arrived the first day. Some may have arrived last week. Some girls arrived without parents and may have been pregnant before entering Texas. Wouldn't you have to prove that a girl got pregnant in Texas to have an issue?
The boys go on work missions as soon as they are able. Upon returning, they often get married. Forget about making statistics work. You have to know the situation of each and every person to know what is happening.

David Friedman said...

On further consideration, my figure of ten children produced at current pregnancy rates is too high. If the total number of children produced by girls 14-17 is two every nine months, then after 4 years about ten children will have been produced by girls who were 14-17 when the children were born. But half of the mothers will by that time be 18 or over. So only about five children will have been produced by mothers who were 14-17 when the child was born and are still under 18 at the end of the four years.

Anonymous said...

Rewind the clock 2 years.

Now the 53 14-17 year olds, are 12-15 years old. Suppose that 29 of those are more or less simultaneously impregnated by men on the compound. (There may in fact be practical reasons for wanting all the children born more or less at the same time in a community-based arrangement like FLDS). Making it simple: over the next year the 29 girls all give birth to one baby each. Now these 29 girls are 13-16 year olds. One year later the cops bust in and take the place down. Now the girls are 14-17 year olds and a medical exam determines 29 of the 53 had been pregnant. What's the problem?

Anonymous said...

Math aside, lets talk about the average underage pregnancy within FLDS. While I agree that the number is not astounding compared with society, we are talking about a very different society. This is not a community where the kids are running amok and having premarital sex on their own, they would be kicked out for that. So what we need to look at is if these girls were forced into this situation, which most likely they were. So while I think the state may have jumped the gun on removing all the children from their homes (I do not believe that all of these children were abused) there is a reason to investigate if children are being forced into marriage. I believe consenting adults can do whatever they want and I take no issue with plural marriage or their religious beliefs. I do take issue with forcing a child or anyone into that lifestyle. I don't think we can ignore the individuals who have left the sect and all say that it is a common practice to spiritually marry underage girls. Again, I don't think the state handled this the best they could, I think they may have done more harm than good. I believe that most of the children will be returned and this will wind up costing the tax payers an awful lot of money for very little. On the other hand maybe they will think twice about forcing young girls into marriage.

Anonymous said...

I think there are several points to be made...first to "try" and apply statistics to this without some kind of base is way off kilter, besides its not about how many are pregnant but how many have been forced into sexual relationships with men 3-4 times there age. Which also leads me to your "quantizing" state statitics with whats going on at YFZ. How many of the pregnant teens in the state had sex with 50'ish men. Not too far off line to say probably like 3 and certainly not 6% of the population as you try to merit. Normal teen prenancies are generally with someone their own age. To say what is going on at YFZ is normal is misleading at the least. These kids live in a world no one should have to...thats the bottom line.

David Friedman said...

"These kids live in a world no one should have to...thats the bottom line."

How do you know what kind of world they live in? You will notice that not even CPS has made a claim about the age of the fathers. The "Fifty year old" man presumably is the fictional husband of the fictional Sara, who turns out to be a 33 year old Colorado woman with no connection to the FLDS outside of her own imagination. The husband in the marriage that Warren Jeffs was convicted of being an accessory to wasn't fifty, he was nineteen.

The point you seem to be missing is that the pregnancy figure is wildly inconsistent with the picture of the group that has been pushed by its opponents and that you have accepted. If that picture is a lie, then you are basing your conclusions about the situation on believing a lie.

Clayton said...

Oh, and it just keeps getting worse... "Official: History of injuries found in polygamist sect children" The article claims that as many as 41 children (out of 461) may have had bones broken or fractured in the past. That would be a nearly 9% rate of bone injuries. Googling "childhood fracture rate" turns up which pegs the childhood fracture rate in an area of the UK at about 4%. It is not inconceivable that the authorities have made a two-fold exaggeration based on the other exaggerations we have been consistently hearing.

Damn those bone-breaking polygamous bastards to hell!

David Friedman said...

With regard to the paper Clayton cited... . I'm not certain, but I think that's a figure for fractures per year, not for cumulative fractures.

Think about your own experience--how many kids in your school at one point or another showed up with an arm or leg in a cast. It's got to be more than 4% over the entire 1-17 age range.

David Friedman said...

In case anyone is still reading this ...

The Texas authorities have now conceded that both of the pregnant "minors" who had children while under their custody were in fact adults, one of them 22 years old.