There is not a truth existing which I fear or wish unknown to the whole HBD community — Chuck
The data in your graph is from two different studies and cohorts and is taken at different times. Are you sure this data is representative? I think the LSYPE uses the actual GCSE that the child took, obtaining them from the school. But we know that all children in England do not take the GCSE. If lower IQ kids at 5 are less likely to take the GCSE that could easily explain the closing of the gap over time.
His point was that I cobbling longitudinal studies together. Others questioned my GCSE data. For example, Matt argued:
GCSE gaps overall seem pretty awful as a general measure of cognitive ability, despite being great for universities, because it is quite possible to take a set of GCSEs in “Art and Design”, “Performing Arts”, “Music”, “Psychology”, “Hospitality”, “Health and Tourism” and “PE”(!).The core GCSEs are English, Maths and Science, which we’d guess have a respectable IQ loading, but the others may be less certain. Those set of GCSEs which have the same content (mathematics and english) as the SAT are probably a good substitute for the SAT (although less than perfect, because, yes, coursework).
Matt’s point was that GCSEs scores, per se, can be misleading and that we should look specifically at Math and Reading test scores, which show relatively high g-loadings. Refer to other points made here. In response — and in followup with a point made by Galtonian — I offer a more recent analysis which circumvents these criticisms. Below are Math and Reading standardized test differences, over the years 1998 to 2007, based on a large cohort (N = 469,848). The scores are relative to a white mean set to zero, with standard deviations of 10:
This confirms my previous conclusion: The Black-White Gaps are trivial to small (in effect size) and don’t increase with age. The data here disconfirms Lynn’s hypothesis. Defenders of this embattled hypothesis need to account for the absence of more than trivial to small gaps, given the large differences between social classes and, more importantly, given the substantial correlation (.7) found between g and these test scores. The Chinese sample, of course, suggests that more than g is involved in population differences — but before you dismiss these achievement scores refer yourself to Gottfredson’s Implications of Cognitive Differences for Schooling Within Diverse Societies, especially table 3 and page 28 to 30. I’m sure that this paper is quite familiar to many of you. In that regards, at very least you have to grant that the near absence of an achievement gap in the UK is as much evidence against a UK IQ gap as the presence of an achievement gap in the US is evidence for a US IQ gap. Hereditarians have routinely argued that the US achievement gap is evidence of an IQ gaps (for example, Rushton and Jensen 2010, section 4), so my evidence should be in good standing.
Dustmann et al., 2011. Ethnicity and Second Generation Immigrants, Chapter 15 in The Labour Market in Winter: the state of working Britain 2010, edited by Paul Gregg and Jonathan Wadsworth, Oxford University Press, 2011