How is work limitation associated with race and ethnicity?

The NHIS collects information on race and ethnicity. In the working-age population 18 to 69, Native Americans report the highest percentage of limitation in work due to chronic conditions -- 17.3% or 262,000 people. Blacks (non-Hispanics) also have a high rate of limitation -- 14.4% or 2.7 million people. Asian Americans reported the lowest levels of limitation -- 5.7% or 311,000 persons. While white non-Hispanics reported work limitations of 11.6% or 14,261,000 people, white Hispanics reported 9.6% or 996,000 people and black Hispanics reported 15.7% or 60,000. These varying rates may be related to cultural and geographical as well as demographic distinctions.http://www.infouse.com/disabilitydata/workdisability/3_5.php