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A New Explanation For the Plight of Winter Babies

Ant passes along a Wall Street Journal report on research that turned up a new explanation for the lifelong challenges experienced by winter babies. "Children born in the winter months already have a few strikes against them. Study after study has shown that they test poorly, don't get as far in school, earn less, are less healthy, and don't live as long as children born at other times of year. Researchers have spent years documenting the effect and trying to understand it... A key assumption of much of that research is that the backgrounds of children born in the winter are the same as the backgrounds of children born at other times of the year. ... [Economist] Mr. Hungerman was doing research on sibling behavior when he noticed that children in the same families tend to be born at the same time of year. Meanwhile, Ms. Buckles was examining the economic factors that lead to multiple births, and coming across what looked like a relationship between mothers' education levels and when children were born." Here's a chart in which the effect — small but significant — jumps out unmistakeably.

25 of 276 comments (clear)

  1. Jumps out? by ucblockhead · · Score: 4, Informative

    Of course the difference jumps out. The chart was deliberately designed to make the change jump out by not using 0 as the origin of the Y axis.

    This is a very common technique for making a difference look a lot larger than it actually is.

    --
    The cake is a pie
    1. Re:Jumps out? by wjh31 · · Score: 5, Informative

      Much more important is the lack of error bars, they are what you can use to decide if the difference is greater than noise. However since they seem to be confident enough to include a secondary maximum and minimum, we are led to assume that the error bars are rather small. Since TFA says the study looked at 52 million children over 12 years, it sounds fairly reasonable to suggest that error bars are relatively small w.r.t atleast the primary max an min.

    2. Re:Jumps out? by ucblockhead · · Score: 3, Interesting

      Yeah, I have little doubt that there is a real effect here, but I hate when things like this are sensationalized. There may well be an effect, but it is a small one.

      --
      The cake is a pie
    3. Re:Jumps out? by Anonymous Coward · · Score: 3, Insightful

      Noise wouldn't be periodic.

    4. Re:Jumps out? by AliasMarlowe · · Score: 4, Insightful

      Did they use only data for Northern hemisphere women (north of the tropics)?, Or is it a mix with tropical and Southern hemisphere as well?

      --
      Those who can make you believe absurdities can make you commit atrocities. - Voltaire
    5. Re:Jumps out? by selven · · Score: 4, Informative

      It's well known that children born in Jan/Feb/Mar are much more likely to get ahead because age cutoffs tend to be January 1, so kids born on Jan 1 compete with kids born on Dec 29 in the same year despite having 11 months more experience. Because of this, more attention is given to these "stars", and they perform higher. You should look at the birth months of some professional football teams.

    6. Re:Jumps out? by icebike · · Score: 5, Insightful

      From TFA:

      The two economists examined birth-certificate data from the Centers for Disease Control and Prevention for 52 million children born between 1989 and 2001, which represents virtually all of the births in the U.S. during those years. The same pattern kept turning up: The percentage of children born to unwed mothers, teenage mothers and mothers who hadn't completed high school kept peaking in January every year. Over the 13-year period, for example, 13.2% of January births were to teen mothers, compared with 12% in May -- a small but statistically significant difference, they say.
      --end-quote

      So problem is more than adequately explained by being born to a teen mother, and winter birth need not be related at all.

      Winter birth is probably attributable to spring break, and the re-emergence of summer fashions (read: skimpy) and horny young guys after a hard winter.

      The real story is births to teen mothers burdens not only the mother, but also the baby. Winter has nothing to do with it.

      --
      Sig Battery depleted. Reverting to safe mode.
    7. Re:Jumps out? by maxume · · Score: 3, Insightful

      Yes, that is the real story. However, there has long been a mystery surrounding why winter babies do not do as well, and the fact that they tend, slightly, to be the children of teen mothers is an interesting explanation (hence the research and the article in the newspaper...).

      --
      Nerd rage is the funniest rage.
    8. Re:Jumps out? by Rob+the+Bold · · Score: 5, Insightful

      Much more important is the lack of error bars, they are what you can use to decide if the difference is greater than noise. However since they seem to be confident enough to include a secondary maximum and minimum, we are led to assume that the error bars are rather small. Since TFA says the study looked at 52 million children over 12 years, it sounds fairly reasonable to suggest that error bars are relatively small w.r.t atleast the primary max an min.

      TFA also says that the 52 million children in the sample were all of them, making the sample 100% of the population. That should result in some pretty small error bars, indeed!

      The two economists examined birth-certificate data from the Centers for Disease Control and Prevention for 52 million children born between 1989 and 2001, which represents virtually all of the births in the U.S. during those years.

      --
      I am not a crackpot.
    9. Re:Jumps out? by quantaman · · Score: 3, Insightful

      Of course the difference jumps out. The chart was deliberately designed to make the change jump out by not using 0 as the origin of the Y axis.

      This is a very common technique for making a difference look a lot larger than it actually is.

      Or it could just be that using 0 as the axis would make a very unreadable graph that wasted a lot of space and didn't show the interesting portion very well.

      Clearly reducing the range has the unfortunate side effect of falsely increasing the perceived significance of the results. However, given that the graphs also very clearly print the mins and maxs I'm strongly drawn to believe that the researchers where actually trying to communicate the data accurately as opposed to tricking unwary readers.

      Oh, and the differences here are a 2.3% decrease in the percentage of married mothers and 1.2% increase in the number of teen mothers. Considering the topic they're analysing the effect is a lot larger than I would have anticipated.

      --
      I stole this Sig
    10. Re:Jumps out? by pla · · Score: 4, Insightful

      Since TFA says the study looked at 52 million children over 12 years, it sounds fairly reasonable to suggest that error bars are relatively small w.r.t atleast the primary max an min.

      With an n of 52 million, those charts do include error bars - They fall about +/- a thousandth of a pixel around each plotted point. The pixels themselves just cover the error bars.

      As for the Y-offset... Yes, you can use that to dishonestly highlight minor difference. When you have such small differences in your dependent variable, however, as long as you make the Y axis entirely clear to the reader, it merely serves to save the viewer a trip to find a magnifying glass.

      Basically, if you had a series that showed some degree of noisy periodicity and you zoomed/cropped in on one section that appears to prove your point, it counts as dishonest. When you have virtually no error and a trend that looks like cookie-cutter copies from year to year - I'd love to see the p values for this, but I'd bet it would require scientific notation to realistically print (ie, on the order of p <= 10^-12).

    11. Re:Jumps out? by davidphogan74 · · Score: 4, Funny

      The moderator was probably born in January, and thus unable to get the question.

  2. That means... by Anonymous Coward · · Score: 5, Interesting

    There's a tendency for promiscuous, uneducated teenagers to have unprotected sex during springtime and early summer. It's always easy to say this, but, duh...

  3. Measured data includes uncertainty by craklyn · · Score: 3, Informative

    Any measurement made requires two peices of information: the measurement and the uncertainty associated with that measurement. To present data as though its known with 100% certainty is misleading and incorrect. It seems pendantic to worry about uncertainty, but when you're dealing with small effects on the order of less than one percent, if the error bars are +/-2.5%, then it's absolutely incorrect to refer to the result as "jumping out".

  4. Re:Born in December by retech · · Score: 5, Funny

    You could do better... if you were born in June.

  5. Different metric by HangingChad · · Score: 4, Interesting

    If you count backward from January, that puts conception around April/May. Right around graduation. So if you suppose the poor and less educated would be getting married and starting a family instead of getting ready for college, that might explain some of it.

    It would probably be just as interesting to track the birth rates correlated to surges in beer and Jagermeister sales.

    --
    That's our life, the big wheel of shit. - The Fat Man, Blue Tango Salvage
  6. Correlation is NOT causation by Anonymous Coward · · Score: 5, Funny

    The real causative in winter babies is that babies born under winter's astrological signs have shorter lifelines.

  7. Conception in July/August by Bwian_of_Nazareth · · Score: 4, Funny

    I see the explanation in the fact that married and educated women have sex with their man only once a year during their holiday in July/August. :)

  8. Winter where? by xirusmom · · Score: 4, Interesting

    I wonder if all the data comes from the North Hemisphere? What happens in the south?

  9. School entrance age cutoffs, maybe? by e9th · · Score: 5, Insightful

    The age cutoff for entry to kindergarten seems to cycle around mid-September, but varies quite a bit from state to state. But in general, a kid born in the winter will have to wait longer to start school.

  10. Re:Unwed mothers? by jonadab · · Score: 3, Informative

    > Unwed? What is this, 1950?

    Statistically, the marital status of the parents is highly relevant to the child's prospects. Children whose parents are married to one another from prior to conception clear through until the child is an adult get on average much better grades in school, are significantly more likely to consistently hold down jobs as adults, make more money on average, are significantly less likely to have a criminal record, are less likely to be smokers, and so on and so forth. These are quite strong correlations.

    Now, correlation is not causation. It's possible that the parent's strong marriage does not *cause* the child's good prospects and performance, but rather that both are caused by some of the same socioeconomic factors. But it's still very much relevant in a statistical study like this.

    --
    Cut that out, or I will ship you to Norilsk in a box.
  11. Re:Born in December by Anonymous Coward · · Score: 5, Funny

    I was born in December and pursuing double masters with GPA of 3.4 is it really bad?

    I was born in June, and received a Ph.D by the time I was 27, with a 3.95 GPA. Luckily for me, part of that Ph.D training involved learning that the word data is not the plural of anecdote.

    It's a good thing, too, because your comment might otherwise serve as the first brick in the foundation of my claim that summer babies are caustic and monumental shitheads that seem to spend their free time in pissing matches.

  12. cause and effect reversed by cinnamon+colbert · · Score: 3, Interesting

    suppose educated women (and education strongly correlates wit income and wealth) "know" htat babies are supposed to be born in the spirng.....
    this would rduce the whole thing to a cultural artifact: well to do parents tell thier kids to have a spring baby, and so it goes...

  13. Re:Unwed mothers? by pgillan · · Score: 4, Funny

    Now, correlation is not causation. It's possible that the parent's strong marriage does not *cause* the child's good prospects and performance, but rather that both are caused by some of the same socioeconomic factors

    I like the idea that it's actually a reverse correlation- that stupid children with poor prospects and bad grades cause their parents' divorces.

  14. Re:Correllation is Not Causation by ceoyoyo · · Score: 5, Informative

    Sigh. Correlation means one of three things with regard to causation. In this case those are:

    a) being born in the winter causes increased risk of health and education problems for the baby
    b) the baby's increased risk of health and education problems causes him or her to be born in the winter (clearly ridiculous)
    c) a third factor causes the baby to both be born in the winter and have increased risk of health and education problems.

    The correlation between birth month and risk of health and education problems has been observed. This study is pointing out that the direct causative option (a) is probably not true since they have found possible third factors (c) that appear to influence birth month and are known to have an effect on the risk of health and education problems.

    In other words, the study is saying, with actual data and without the childish, misunderstood slogans, the same thing you are - birth month does not cause increased risk of health and education problems.

    Showing correlation is required for establishing a causative link between two observations so no, correlation studies do not "need to die." It would be nice if people (including you) understood them a little better though.