The lack of Social Security filings is a bit of a mystery for Laura Quinby, a senior research economist at the Center for Retirement Research. Older Americans often feel the need to apply for benefits in person, so the closure of the Social Security Administration's local offices during the pandemic might have dissuaded some from applying.

https://www.bloomberg.com/news/articles/2022-03-23/the-great-retirement-disconnect-that-puzzles-u-s-economists?sref=EcccZSTc