When people enter or reenter the labor force and begin to search for a job, that is generally a good thing even though at the margin their entry tends to increase the unemployment rate (or prevent it from declining). Beginning in the 1960s, labor force participation rose steadily as women entered the paid workforce (figure 4).
That trend ran its course as participation peaked around 2000 and has declined steadily since then as a result of the aging of our population and other longer-run trends, notably the decline in participation by men in the heart of their working-age years.