Healthcare financing involves varying distributive effects and builds on different concepts of solidarity. We suggest a set of indicators to explore equity issues in healthcare financing using aggregate spending and revenue data: the Index of Risk and Income Solidarity (IRIS). Contrary to established indicators, IRIS compares eleven OECD countries over four decades. In terms of risk solidarity we observe upward convergence. By contrast, the average and the variance of income solidarity remain fairly stable over time. The expected reform pattern of increasing risk solidarity and reduced income solidarity is only observed in the Netherlands and Switzerland. Yet, this reflects country-specific political compromises rather than assumptions about the effects of health spending growth and global competition on income solidarity.