Introduction A growing number of countries are developing or reforming pension and health policies in response to population ageing and to enhance the welfare of their citizens. The adoption of different policies by different countries has resulted in several natural experiments. These offer unusual opportunities to examine the effects of varying policies influencing health. Realising these opportunities requires harmonised data-collection efforts. Methods An increasing number of countries have

more »

... agreed to provide data harmonised with the Health and Retirement Study in the United States. This article discusses these data sets, including their key parameters of health status, research designs, samples, and response rates. It also discusses the opportunities they offer for cross-national studies and their implications for policy evaluation and development. Results The HRS family of surveys shares a common research design and collects comparable micro-data with a common goal to better understand the multifaceted lives of older individuals and their families and to track and identify changes over time. As the longitudinal data from harmonised HRS surveys accumulate, their scientific value will grow with the research opportunity to examine longitudinal changes in health and its determinants. Armed with knowledge about causal relationships, researchers can also use longitudinal, cross-country data to simulate what might happen under different policy scenarios. As policy reforms continue, researchers can use panel data to identify how the adoption of a policy reform launched in one country might be applied in another country, and the implications of such policies for health outcomes.