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Matt Rosenberg

Male to Female Birth Ratio Reduced in U.S. and Japan

By April 17, 2007

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While there are typically more males born in a given population than females (the ratio is usually 105 males for every 100 females), in the United States and Japan, the number of males per 100 females has been declining. Reuters reports, based on study results, that the decrease is likely due to exposure to environmental pollutants. The data shows that, "In the U.S., the proportion of boys dropped from 105.5 per 100 girls in 1970 to 104.6 in 2001; in Japan, the male-to-female ratio dropped from 106.3 boys for every 100 girls to just fewer than 105 per 100."


April 23, 2007 at 10:55 am
(1) Annette Baillargeon says:

Did anyone ever think that abortion may have anything to do this? How many thousands of babies a re murdered every year. Maybe just maybe we would find the missing children in the grave.

April 20, 2011 at 5:08 pm
(2) jack.harper says:

I dont know how familiar you are in your studies of Abortion, but most dont know the Sex of the fetus, until after it is aborted…..so with that stated, the proportions aborted would equal the same as stated above(105 per 100)..there must be other factors besides personal feelings!

April 26, 2007 at 6:54 am
(3) Matt Rosenberg says:

Hi Annette! Thanks for your post! However, I’m not sure how abortion would modify the sex ratio of males to females.

November 6, 2011 at 12:19 pm
(4) dave says:

In China, due to cultural influences, the availability of ultrasound, and the one child policy, there are over 160 boys born for every 100 girls. So about 1 in 3 girls are being aborted because they are girls. With this in mind, it’s not tough to imagine that about 1 in 100 boys in the US or Japan isn’t being born because they are male.

April 27, 2007 at 7:19 am
(5) shobana ramkumar says:

what are seemingly advantages are really disadvantages. the permafrost melting would probably give rise to malaria there. you could create a schools network on your site across the world I am from india and iam sure many people across the world will benefit from better awareness.

May 4, 2009 at 6:40 pm
(6) Catherine says:

I think that if planned births have a higher result of girls over boys – ie people trying have intercourse before ovulation which would increase the chance of having a girl since Y sperms live longer…than the trend of higher educated parents and people delaying child bearing will continue to impact this ratio as well as the ratio of boys to girls in a specific setting such as higher educated parents from a higher socio economic background. Especially with first born children, the ratio of girls to boys among our friends is extremely high.

September 15, 2009 at 9:28 pm
(7) zorro says:

internet pornography plays a vital role in this subject, how many people in the world replace masturbation with procreation.

October 16, 2009 at 7:32 am
(8) ORLY says:

Who Cares most of us guys don’t get laid cause we don’t try and when we do its sexual harrasment this sexual harrasment that or that guys creepy but he only said hello some people take it to not just guys, Internet porn RULESSSSS im downloading it now…

May 22, 2010 at 6:48 pm
(9) BryAnime says:

Well, I for one would prefer the gender ratio to be closer to 50/50. What about those 5 guys (out of 105) who don’t have a match, huh?

May 28, 2010 at 4:11 pm
(10) Christine says:

The correlation between abortion and the birth raito is simple Mr. Rosenburg. Ask any woman who has raised a boy and a girl. They will tell you that boys require more energy, influence, and direction than girls. Ask any single mom (who has a boy and girl) who is suddenly faced with pregnancy, which they would prefer boy or girl. Based on the difficulty, I submit to you that some abortions are influenced by gender.
In addition since the advent of birth control, couples have been frequently asked how many children they want, which never would’ve been asked prior to birth control, it would’ve been a moot question. However, more recently since abortion has become more acceptable, couples are frequently asked what they want boy or girl. Again a moot question 30 years ago. These subtle questions infer a right to decide how many and which one they want or dont want, which leads to selection. I again submit to you that some abortions are influenced by gender based on the desires of couples.
This brings up my last point, go to any fertility clinic. Whether you are getting IVF or AI, they can give you what gender child you want. Not 100% of course, but greatly increased chances, it’s called sperm sorting. Also, once you have implanted embryos, if there are more than you bargained for, you can have selective abortions determined by the gender. Now, visit any fertility forum and you will find most of the members want a girl. Hey, that is a good idea, why dont you join a few and put forth a poll, most forums have polling capabilities. For that matter, join several single mom forums too and poll them. I think you will find that girls are preferred over boys. Where there is a preference and the possiblity of selection (abortion), ratios will be affected.
I do not think that this is the only influence on the ratio, but it is one worth mention. I would love to see a follow up article on this! Have a great day.

May 28, 2010 at 4:33 pm
(11) Christine says:

BryAnime, the male to female birth ratio is important to maintain because of the higher statistic of premature deaths for boys; through premature birth, violence, and fatal accidents. Premature girls are more likely to survive than boys. Violence: fights, gangs, and war. Fatal accidents: guns, motorcyces, extreme sports,… etc. Google any of that info, there is plenty out there about it.

June 7, 2010 at 1:42 pm
(12) katelynn miller says:

do they really send ur kid to a foster home or somethim if u have two kids r u aloud to put one up for adoption an then have a nother??????????????????????????????????????i am veryy confused

July 15, 2010 at 1:19 pm
(13) Adrita says:


August 4, 2010 at 11:03 pm
(14) Just Saying... says:

Obviously not everyone wants a girl.


September 12, 2010 at 2:51 am
(15) Ron says:

Catherine says: “since Y sperms live longer”

The “Y” sperm is the male sperm and anything male does not live as long as the female. The male is the weak sex throughtout every species including humans. That is why 150 males are conceived for every 100 females but by birth, 45 of the males will have died. As to the 105 males per 100 girls, by the time they are 16 or 17, the sex ration is 50/50 as more males die at every age than do women. This higher death for males goes on throughout life so at 80, there are twice as many women as there are males.

September 12, 2010 at 3:14 am
(16) Ron says:

Just Saying… says:
Obviously not everyone wants a girl.

When the nation was mostly farmers, most wanted boys as they would help on the farm. When there were fewer farms, it was almost equal between those who wanted boy vs those who wanted girls. Now that girls are being given the same chance as boys to suceed, there are more who want girls as we can now see that girls can do everything the boys can do and as we see girls get better educations, and we see girls outperforming the males on every front, I think even more people will opt to have girls but if someone really does want a girl, all they need to do is move to one area of Canada where there are 3 girls being born for every male. This is due to heavy polllution in the area which as in most places, often kills the males far more often even before they are born.

December 14, 2011 at 10:25 pm
(17) Shannon says:

Male babies are fragile (genetically speaking). So although the ratio may be about 50/50 at conception, slightly more female babies should actually be born, or actually survive the first few months of life. Ron (15), you have it correct.

April 10, 2012 at 6:59 am
(18) Cascara says:

@shannon, the Y-chromosome carrying sperms are lighter than the XX-sperm, bc the Y-chromosome is tiny compared to the X, so an XY-combination plus 22 other chromosomes weights less, so there are much more male conceptions. XY-combinations, aka males, are vulnerable to mutations in the X-chromosome, since they don’t have a pair of X’s where the probability of having the same mutations of same alleles is small, so they can only produce the proteins encoded in the only copy they have, without backup. Even at the time of embedding a week after conception a lot of the male embryos have failed in the first cell divisions and forming gastrulation, so the mother will never know of the conception and have a normal menstruation. After embedding it’s also common that something goes wrong genetically, for both sexes, but more so for males, so by the time of birth the enormous male overrepresentation in conception has decreased to 51 vs. 49 % males – females. This is just how human procreation works, it has nothing to do with innate supremacy of either gender. The so-called male vulnerability actually helps every generation screen out the worst mutations.
But otherwise Shannon got it right, baby boys have a much bigger risk of unexplainable infant deaths and such, where the baby simply forgets to breathe while sleeping. :,,(

April 20, 2012 at 9:43 am
(19) jake says:

excuse me dave, but im doing a project on gendercide for model UN. I have done very extensize research on cites like the CIA factbook. The highest ratios are 130 boys to 100 girls, and thats only in a few provinces in China. You must have pulled 160-100 out of your ass because there isn’t a single site that verifies is anywhere. if the ratios were at 160-100, the survival of Humanity would be at serious risk. For all you saying adoption is murder, our planet is already overpopulated. The baby would be unwanted anyways, and it costs money to put a child into adoption and a lot of money to have the Birth. So no, its none of your business. It’s only the mother and fathers business and please shut up about it, noone cares.

April 21, 2012 at 1:37 pm
(20) Zach says:

You know it has been shown in a number of studies in US, UK and Canada that OCP’s are changing our fish populations. The birth control gets into our freshwater supply when people use them and then extra hormones are excreted from their urine or when they throw their medications out. The hormones are not filtered by our current system. Here is one account of fish caught near Boulder, Colorado “When they netted 123 trout and other fish downstream from the city’s sewer plant, they found 101 were female, 12 were male, and 10 were strange “intersex” fish with male and female features.”

Maybe a similar phenomenon is occurring in our own population because birth control contaminating our water supply and it is changing our male to female live birth ratio.

July 24, 2012 at 5:21 am
(21) Michael J. Trout says:

Why is birthrates falling for males globally? It is new powerful, water soluble, systemic pesticides invented in the 1990s and now have reached market diffusion globally. They can NOT be washed off and are not in most of our food. And nearly all promote estrogen and decrease testosterone.

They are chemically castrating males.

September 22, 2012 at 4:10 am
(22) Ali says:

feminist revolution has caused this….females trying to dominate over men and trying to be equal to them has caused this..this can never happen cos in all religions god has always said that man is dominent over women and if women try to empower men then this is how god will punish us…God says tht a time will come when mothers will be treated like dogs and husbands will be disrespected and during this time the population of men to women will become 1 is to 50 i.e i man for every 50 women.

January 26, 2013 at 4:43 pm
(23) kage says:

Ok, so just to point it out, while males do have a tendancy to die more easily of a premature death and often females outlive them, this has very little to do with the decline. Mind you, the decline is small and has yet to affect anything but sexist people or the butt-hurt members of society and the overdramatic who think the human population is going to shift from a TOTALY NATURAL PHENOMENA regarding gender influxes. I mean, a few decades ago the japanese gender ratio was backwards; males outwighed females almost 107-100 and no one was complaining then. ):l

March 27, 2013 at 9:13 pm
(24) hey says:

What about war too. If going by census.

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