Changes in the ratio of the age groups 15 to 64 years and >64 years in different countries. In all countries shown, the demographic change will cause a major shift in the ratio of the age groups between 15 to 64 years and >64 years, which reflects the ratio of the main blood donor population vs the main blood recipient population. The demographic change is most pronounced in the eastern German state of Mecklenburg-West Pomerania, which can be seen as a model region where the effects of the demographic change on the blood supply manifest 10 to 15 years earlier than in other regions. The figure is grouped into 4 panels that summarize countries with similar changes in demography. The countries are listed according to the ratio between age groups in 2030 from the highest to the lowest ratio. The hatched line shows the change in the population ratio in Mecklenburg-West Pomerania; the numbered horizontal lines show at which year the population ratio of Mecklenburg-West Pomerania exemplifies the population ratio reached in 2030 for the extremes in each group. The other countries of each panel show effects in between. Supplemental Table 1 provides the respective data.