Federal Reserve policymakers, who are looking to estimate inflation in preparation for rate increases, are studying a new Bureau of Labor Statistics report that indicates that the reasons that people stay out of the workforce have changed over the last decade. 35% of Americans were not part of the workforce in 2014, an increase of almost 4% since 2004. More people in all age groups cited “retirement” as a reason for not actively seeking employment, with the number of 20-24 year olds who have retired doubling since 2004. Other reasons for not working include men with increased home responsibilities, an increased number of male veterans with service-related disabilities, and women who have retired due to illness or school.
See "Yellen's Job Puzzle: Why Are 20-Somethings Retiring?", Kasia Klimasinska, Bloomberg Business, January 4, 2016