An interesting statistic is the relative percentage of the US population of working age (say ages 25-64 to be conservative) and 65 and over, based on US Census Bureau data and projections. The percent of the population age 65 and over is about 15% now, but expected to grow to 24% by 2060. This has implications for how the OASDI (Social Security) program is funded.
Link: https://www.census.gov/content/dam/Census/library/publications/2015/demo/p25-1143.pdf