According to the Max Planck Institute for Demographic Research, "demographic change describes the changes in population size and structure caused by changes in birth rates, death rates, and by migration. Demographic change in the Western developed countries of today is marked by low birth rates below population replacement and by rising life expectancy. The result is that populations are aging and shrinking. And migration may overlap with these developments. Migration, for example, leads to further population reductions in the regions of origin and to attenuation in the regions of destination. And if it is the young rather than the old who migrate from a region, aging is exacerbated in the region of origin."