Huh, glad you dug into that. Below that chart they link the youth rates, and they're way down. Teenage labour force participation peaked in 1978, with a mini peak in 1989, and 20-24 in 1989, with a mini peak in 2001.
The answer there is likely we're keeping them in school longer + filling downtime with school or social media or "extracurriculars". Alongside a growing NEET cohort that doesn't feel motivation to do anything or is disabled.
As for 55+, I'd be very interested to see the relative age distribution within that pool over that period. I suspect there's a lot more 65+ within the pool now than when the rate was higher. That trend is set to grow.
The answer there is likely we're keeping them in school longer + filling downtime with school or social media or "extracurriculars". Alongside a growing NEET cohort that doesn't feel motivation to do anything or is disabled.
https://fred.stlouisfed.org/series/LNS11300036
https://fred.stlouisfed.org/series/LNS11300012
As for 55+, I'd be very interested to see the relative age distribution within that pool over that period. I suspect there's a lot more 65+ within the pool now than when the rate was higher. That trend is set to grow.