A friend of mine recently became pregnant one of the more woo things she has come out with is Chinese Birth Charts.

On the admittedly tiny data set of 5 the chart was 100% accurate.

Chinese Birth Charts


I in no way believe this can be 90% accurate as some claims make out. But I'd like to see some studies.

Can any one please point me to studies/papers that prove one way or another.

  • It's not accurate for my son... I doubt though that anyone would waste time to study (or accept a paper) on this kind of stuff. – Sklivvz Feb 28 '11 at 20:29
  • It's 75% accurate for me, but I would suggest that that is in line with standard deviation with such a small sample (4 in this case) – Ardesco Apr 20 '11 at 13:50
  • Astrology (or, to be pedantic, belief in astrology) affected births in nearby Japan markedly in 1966: en.wikipedia.org/wiki/Demography_of_Japan – Andrew Grimm Dec 29 '18 at 7:51
  • I find it funny that an (unnamed) Chinese scholar from the 13th century bothered about women given brith at age 40-45 but not at age 13-17... Also, should we read the chart using the age of the mum during conception or when giving birth ? – Evargalo Jan 2 at 14:03

I found this website and several others with very similar text which describes the hypothesis.

It talks about male and female sperm carrying opposite electrical charges, and the female ovum cycling between positive and negative charges thus determining which sperm can fertilize it. Apparently this cycle is synchronized for all women everywhere and thus can be conveniently charted.

The page also talks about some research that confirmed this hypothesis, including one that said that sperm were either attracted to cathodes or anodes depending on whether they carried an X or Y chromosome. I found this bit on sperm sorting which describes labeling the sperm with a dye that attaches to DNA (and X chromosome has more DNA so will fluoresce more brightly), and then attaching a charge to each one using a single droplet of charged fluid, before sorting them. I suspect this method was confused as the sperm already carrying a charge.

The only thing that differs between male and female sperm is the DNA they are carrying. They do not only carry an X or Y chromosome, they carry fully half of the entire human genome, including one of the sex hormones. If the X and Y chromosomes have opposite charges, what charge do the rest of the chromosomes have? What happens when an X and Y chromosome are combined in a cell nucleus--do they tear through the rest of the genetic soup to snap together like fridge magnets? DNA is all made of the same stuff and the charge carried by each chromosome is the same (that is, none), so this theory can't possibly be true.

The real odds of this chart are 50%, the same as all the other outside-the-genetic-laboratory sex selection techniques.

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    "real odds of this chart are 50%, the same as all the other outside-the-genetic-laboratory sex selection techniques" - citation required. (Because it isn't true, because babies aren't 50% male.) – Oddthinking Dec 29 '18 at 9:35
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    @oddthinking it’s accurate if you’re rounding to the nearest ten percent, ie only one significant figure. – Andrew Grimm Dec 29 '18 at 19:54
  • The sperm sorting technique you said confirmed the hypothesis did nothing of the sort. The technique described is not based on any "inherent" charge of male or female sperm but purely on the different size (x and Y chromosomes are very different in size). There is no easy biological way to switch the preference from male to female. – matt_black Dec 29 '18 at 21:37

It's easy to see that the predictions don't make any sense:

  1. The ratio of boys to girls born is well known: 105 boys versus 100 girls.

    In other words we should see 172 "B" and 164 "G". Instead we see 162 "G" and 174 "B" and hence a ratio of 107 boys versus 100 girls.

    Surely, then this calendar can't account for the measured data.

    Note: this points assumes an overall uniform birth rate over the age of mothers and months of conception. As such it is as correct as this assumption.

  2. The ratio of sexes at birth is almost independent of the age of the mother. The calendar predicts something like this graph: enter image description here

    As you can see it is completely inconsistent...

  3. If there was any truth to the calendar, then why would a different source show a completely different calendar?

As a (amusing?) side note. If one was to always predict a boy, they would be right 51% of times! More than random chance :-)

  • 3
    Regarding #1, you're assuming an even distribution of conception dates. Likely a logical assumption if your data set is as large as the population of the world, but who knows, maybe certain days of the week have higher conception rates? – keithjgrant Feb 28 '11 at 22:55
  • @Keith: correct. I should specify that. – Sklivvz Feb 28 '11 at 22:57
  • I do not know whether the diamond moderator Sklivvz would approve of an answer being based on logic :) skeptics.meta.stackexchange.com/questions/1019/… – Andrew Grimm Dec 29 '18 at 7:42
  • The answer is based on facts: the ratio of boys to girls needs to be the same as the real one; it needs to be almost independent of the age of the mother; predictions need to be consistent. Point 1 and 2 are based on the wikipedia link, point 3 has its own source. – Sklivvz Dec 29 '18 at 16:52

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