"This means that factors shared within families, such as sibling-shared genes, childhood socioeconomic status, parental education, or other shared family experiences, cannot account for the findings."
Oh yes they can! The authors are making the same mistake they made in their earlier paper on the reverse Flynn effect. They are forgetting that Norwegian siblings are increasingly half-siblings. Among Norwegian women with only two children, 13.4% have had them by more than one man. The figure rises to 24.9% among those with three children, 36.2% among those with four children, and 41.2% among those with five children (Thomson et al., 2014). If siblings have different fathers, they cannot share the same genetic background.
Who are the fathers of the younger siblings? The sort of men that single mothers often end up with, men of the lowest educational level:
"At age 45, about 15 percent of all men in the 1960-62 cohort with a compulsory education had had children with more than one woman, compared to about 5 percent among men with a tertiary degree. If looking at fathers only (Figure 6), the pattern becomes even more pronounced. At the lowest educational level, 19.3 percent of those who had become fathers had children with more than one woman, compared to 6.1 percent of those at the highest educational level. (Lappegård et al., 2011)"
Thomson, E., Lappegård, T., Carlson, M., Evans, A., and Gray, E. (2014). Childbearing across partnerships in Australia, the United States, Norway, and Sweden, Demography 51(2), 485-508. https://doi.org/10.1007/s13524-013-0273-6
Paper says "Demographics come from the population register, containing birth year and parental identifiers that allow for the identification of siblings.", so they presumably used both parents IDs, so these are full siblings, not half-siblings.
It is now common practice in Norway for a stepfather to adopt his wife's children. At that point, he becomes the "father" for all intents and purposes. This has been the case since 1986, when Norway passed The Adoption Act: "If a spouse or cohabitant has adopted a child of the other spouse or cohabitant, the said child shall have the same legal status in relation to both spouses or cohabitants as if he or she were their joint child." The Adoption Act (1986), Chapter 3, Section 13.
This paternity issue affects different registers to different degrees. The family register is most vulnerable. It is updated annually and thus identifies the current legal father as the “father” (Black et al., 2011, note 4). The birth register is least vulnerable. The mother will usually identify the biological father as the "father." The exceptions are cases of infidelity or cases where a new relationship has formed during the pregnancy and the stepfather wishes to be recognized as the child's father.
Bratsberg and Rogeberg (2018) were most interested in the conscript register. This was where they obtained their IQ data. They then used the family register to locate the conscript's brother or brothers, at which point they returned to the conscript register to find that person's IQ. The family register, however, will most likely identify a stepfather as a "father." One would have to go back to the birth files and double-check, but this doesn't seem to have been done.
When I discussed this issue with one of the co-authors, Ole Rogeberg, he replied that very few of the brothers could be half-brothers because the correlation between brothers for IQ was 0.47, and this figure is similar to a previously published estimate of 0.49 for inter-sibling correlation (Paul 1980). That estimate, however, is largely based on American whites, who are a more heterogeneous population than native Norwegians.
References
Black, S.E., P.J. Devereux, and K.J. Salvanes. (2011). Older and Wiser? Birth Order and IQ of Young Men. CESifo Economic Studies 57(1): 103-120.
Bratsberg, B., and O. Rogeberg. (2018). Flynn effect and its reversal are both environmentally caused. Proceedings of the National Academy of Sciences Jun 2018, DOI: 10.1073/pnas.1718793115
It is interesting. I think I read somewhere that the genetic iq of the population is going and that it is not purely due to immigration. But here we see that high iq men seem to have higher fertility rate. Is the decrease in iq due to high iq women not having children? Maybe lower iq men cucking other men or having children that they are unaware of?
I wonder how much we can trust self-reported children count of men with low IQs. It's comparatively easy for a man to have a child they don't know about. It would be nice to compare average self-reported number of children by women and see if they are same.
The lowest-IQ men having the fewest children appears to be a quite recent phenomenon happening across the Western world, especially after Covid, with birth control apparently making its way down into the <85 IQ types, and thereby appearing to disprove the assumption that they’re too stupid to adopt birth control methods.
Low status and low IQ, unfortunately, aren't the same thing, as anyone who notices the de facto status of African Americans in the United States will point out.
Emil's study here attempts to look specifically at IQ.
"This means that factors shared within families, such as sibling-shared genes, childhood socioeconomic status, parental education, or other shared family experiences, cannot account for the findings."
Oh yes they can! The authors are making the same mistake they made in their earlier paper on the reverse Flynn effect. They are forgetting that Norwegian siblings are increasingly half-siblings. Among Norwegian women with only two children, 13.4% have had them by more than one man. The figure rises to 24.9% among those with three children, 36.2% among those with four children, and 41.2% among those with five children (Thomson et al., 2014). If siblings have different fathers, they cannot share the same genetic background.
Who are the fathers of the younger siblings? The sort of men that single mothers often end up with, men of the lowest educational level:
"At age 45, about 15 percent of all men in the 1960-62 cohort with a compulsory education had had children with more than one woman, compared to about 5 percent among men with a tertiary degree. If looking at fathers only (Figure 6), the pattern becomes even more pronounced. At the lowest educational level, 19.3 percent of those who had become fathers had children with more than one woman, compared to 6.1 percent of those at the highest educational level. (Lappegård et al., 2011)"
References
Lappegård, T., Rønsen, M., and Skrede, K. (2011). Fatherhood and fertility. Fathering, 9(1), 103-120. https://doi.org/10.3149/fth.0901.103
Thomson, E., Lappegård, T., Carlson, M., Evans, A., and Gray, E. (2014). Childbearing across partnerships in Australia, the United States, Norway, and Sweden, Demography 51(2), 485-508. https://doi.org/10.1007/s13524-013-0273-6
Paper says "Demographics come from the population register, containing birth year and parental identifiers that allow for the identification of siblings.", so they presumably used both parents IDs, so these are full siblings, not half-siblings.
Emil,
It is now common practice in Norway for a stepfather to adopt his wife's children. At that point, he becomes the "father" for all intents and purposes. This has been the case since 1986, when Norway passed The Adoption Act: "If a spouse or cohabitant has adopted a child of the other spouse or cohabitant, the said child shall have the same legal status in relation to both spouses or cohabitants as if he or she were their joint child." The Adoption Act (1986), Chapter 3, Section 13.
This paternity issue affects different registers to different degrees. The family register is most vulnerable. It is updated annually and thus identifies the current legal father as the “father” (Black et al., 2011, note 4). The birth register is least vulnerable. The mother will usually identify the biological father as the "father." The exceptions are cases of infidelity or cases where a new relationship has formed during the pregnancy and the stepfather wishes to be recognized as the child's father.
Bratsberg and Rogeberg (2018) were most interested in the conscript register. This was where they obtained their IQ data. They then used the family register to locate the conscript's brother or brothers, at which point they returned to the conscript register to find that person's IQ. The family register, however, will most likely identify a stepfather as a "father." One would have to go back to the birth files and double-check, but this doesn't seem to have been done.
When I discussed this issue with one of the co-authors, Ole Rogeberg, he replied that very few of the brothers could be half-brothers because the correlation between brothers for IQ was 0.47, and this figure is similar to a previously published estimate of 0.49 for inter-sibling correlation (Paul 1980). That estimate, however, is largely based on American whites, who are a more heterogeneous population than native Norwegians.
References
Black, S.E., P.J. Devereux, and K.J. Salvanes. (2011). Older and Wiser? Birth Order and IQ of Young Men. CESifo Economic Studies 57(1): 103-120.
ftp://193.146.129.230/pdf/papers/pew/PaulDevereux.pdf
Bratsberg, B., and O. Rogeberg. (2018). Flynn effect and its reversal are both environmentally caused. Proceedings of the National Academy of Sciences Jun 2018, DOI: 10.1073/pnas.1718793115
https://sci-hub.tw/https://doi.org/10.1073/pnas.1718793115
Government of Norway. (1986). The Adoption Act. Act of 28 February 1986 No. 8 relating to adoption,
https://www.regjeringen.no/en/dokumenter/ACT-OF-28-FEBRUARY-1986-NO-8-RELATING-TO/id443477/
Paul, S.M. (1990). Sibling resemblance in mental ability: a review. Behavior Genetics 10(3): 277-290.
https://pdfs.semanticscholar.org/eda5/6485400cdddc1b974b9db6edf74acb28fb23.pdf
It is interesting. I think I read somewhere that the genetic iq of the population is going and that it is not purely due to immigration. But here we see that high iq men seem to have higher fertility rate. Is the decrease in iq due to high iq women not having children? Maybe lower iq men cucking other men or having children that they are unaware of?
I wonder how much we can trust self-reported children count of men with low IQs. It's comparatively easy for a man to have a child they don't know about. It would be nice to compare average self-reported number of children by women and see if they are same.
Here they talk about the increasing gap between the number of childless women and men, and also look at immigration: https://www.sciencenorway.no/children-and-adolescents-demography-gender-and-society/why-are-fewer-men-becoming-fathers-than-before/1767348
The lowest-IQ men having the fewest children appears to be a quite recent phenomenon happening across the Western world, especially after Covid, with birth control apparently making its way down into the <85 IQ types, and thereby appearing to disprove the assumption that they’re too stupid to adopt birth control methods.
It is not a recent phenomenon that low status men have fewer children than the high status men.
This is why you have twice as many foremothers as forefathers; Some women have children with men who have children from previous relationships.
Low status and low IQ, unfortunately, aren't the same thing, as anyone who notices the de facto status of African Americans in the United States will point out.
Emil's study here attempts to look specifically at IQ.