Spatial Projections of Age-Structured Populations
Erich Striessnig1, Jing Gao2, Brian O'Neill2, Leiwen Jiang3
1Wittgenstein Centre for Demography and Global Human Capital (IIASA, VID/ÖAW, WU), Vienna, Austria. 2National Center for Atmospheric Research (NCAR), Boulder, USA. 3Asian Demographic Research Institute (ADRI), Shanghai, China

Abstract
In recent years, both the availability and use of population information in climate change impact assessments have greatly improved. One important milestone in this direction were the Wittgenstein Centre’s multi-dimensional cohort-component projections of national populations by age, sex, and level of educational attainment (Lutz, Butz, and KC 2014). They provide the “human core” of the shared socioeconomic pathways (SSPs) (KC and Lutz 2017; O’Neill et al. 2015) that have since been spatially disaggregated (Jones and O’Neill 2016), yet without the aforementioned sociodemographic characteristics already included in the SSPs. The main objective of this paper is to add age-structure to these spatial projections. Using data from U.S. censuses, we analyze the degree of spatial variation in the age structure of the U.S. population dating back to 1940. Once a firm relationship between the age- and the spatial-distribution has been established, this will serve to calibrate the projection model.