The Air Force has selected 479 airmen for promotion to chief master sergeant, the Air Force Personnel Center said in a release Tuesday.

There were 2,241 senior master sergeants eligible for promotion this year, AFPC said, which means the selection rate for E-9 is 21.37 percent. That is slightly lower than the 22.04 percent E-9 selection rate last year, and a larger drop from the three-decade selection rate high of 23.82 percent that was hit in 2016.

But the selection rate is still higher than the lean years of 2013 to 2015, before and during the drawdown, when selection rates ranged from 18.97 percent to 20.83 percent.

The Air Force selected 472 airmen for promotion to chief master sergeant last year, and 531 in the boom year of 2016.

AFPC said it will release the list of selectees the morning of Dec. 6, but their commanders will be notified starting on Thursday. That way, commanders can prepare to give their airmen the good news one day before the public release.

Promotions of the new chief master sergeants will begin in January, according to their promotion sequence number.