Six years later, more than 20 million people have gained health coverage thanks to the Affordable Care Act (ACA). While this is an achievement worth celebrating, millions continue to go without health insurance and finding them can be difficult due to lacking data from previous enrollment periods. Are all communities and groups being counted in enrollment surveys? Who is left out? It will not be easy to identify these communities without access to important data collected by health insurance Marketplaces. Without this data, people who are often excluded or ignored from health care efforts — like smaller racial and ethnic groups, immigrants and limited-English speakers — will continue to be left out.