The short answer is bone densities are higher for black than for whites.

See: Racial Differences in Bone Density between Young Adult Black and White Subjects Persist after Adjustment for Anthropometric, Lifestyle, and Biochemical Differences
Bruce Ettinger et al., Jour Clinical Endocrinology & Metabolism, Vol. 82, No. 2, pp. 429-434, 1997.

http://jcem.endojournals.org/cgi/content/full/82/2/429

One conclusion is that "The lower lifetime risk of hip fracture among black persons (*ref.) results at least partly because American black women (*refs.) and men (*refs.) achieve 5%-15% greater peak bone mass than white persons."
*cited references

Graphs of the differences shown here:
Bones in Different Races.

http://depts.washington.edu/bonebio/bonAbout/race.html

This article states that "Asian persions tend to have bone density that is as low or even lower than Caucasians. Hispanic people have bone density that is about the same or a little bit higher than Caucasians."