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FIGURE 3-19  Projected weighted support ratio with probability bounds and 20 illustrative stochastic trajectories, 2010–2050. The central dark line is the median committee forecast. There is a 50 percent probability that the support ratio will lie between the blue dashed lines in future years and a 95 percent probability that it will lie between the green dashed lines. The figure shows 20 trajectories. The actual projection is based on 1,000 sample paths. For the method used, see Appendix A. SOURCE: Donehower and Boe (2012).

thirds chance that the decline will be between 9 percent and 16 percent, and a 95 percent chance that it will be between 5 percent and 19 percent. We can conclude from the stochastic approach in Figures 3-18 and 3-19 that it is virtually certain that the U.S. will experience substantial population aging and that the support ratio is virtually certain to fall in the coming decades. The expected decline of 12 percent translates into an average yearly rate of decline of one-third of 1 percent (0.33 percent).



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