Rapid increases in employer-sponsored health insurance premiums are a growing concern for policymakers. Given this concern, it is important to understand how these premium costs are distributed across employees. We use newly available tax data to shed light on the distribution. More specifically, employers with more than 250 employees are required to report the total premiums paid by both employers and employees to the IRS on Form W-2. We are the first to use employer-employee-linked administrative data to measure the distribution and correlates of health insurance premiums in the United States.