but the expectancy of a working-age adult ... has barely budged since before Social Security was invented. Lifespan from birth ... has risen almost entirely due

but the expectancy of a working-age adult ... has barely budged since before Social Security was invented. Lifespan from birth ... has risen almost entirely due to lower infant mortality. This is not true. While it's true that infant mortality rates in industrialized countries have decreased a lot since the 1930s, so have mortality rates at every age.