The paper is pretty straightforward, Copy number variation in African Americans:
Employing a SNP platform with greater than 500,000 SNPs, a first-generation CNV map of the African American genome was generated using DNA from 385 healthy African American individuals, and compared to a sample of 435 healthy White individuals. A total of 1362 CNVs were identified within African Americans, which included two CNV regions that were significantly different in frequency between African Americans and Whites (17q21 and 15q11). In addition, a duplication was identified in 74% of DNAs derived from cell lines that was not present in any of the whole blood derived DNAs.
Also see ScienceDaily. The authors are interested for purposes of disease, one of the loci which exhibit a CNV difference seem to be related to a variant of mental retardation. They suggest that differences between whites and blacks on this locus might be due to difference in the frequency of duplication between the two groups (45% vs. 8% respectively). Though remember that we have a non-pathological example of CNV polymorphism in human populations. As the field gets saturated by analyses of SNPs one assumes that there will be more investigation of other types of genetic variation, such as CNVs.