To study trends in disparities over time, consistent race and ethnicity variables are necessary. The federal government has tried to develop more sensitive variables over time, but also preserve the ability to examine longitudinal trends. The Census Bureau, Office of Management and Budget, Institute of Medicine and Department of Health and Human Services have all grappled with this issue. The current HHS standards for collecting disparities data is provided in Appendix A. The Affordable Care Act mandated that these data variables be included in all federal health surveys. More information on these standards is included in Section 5.2.1.