The following is the Feb. 9, 2023, Congressional Budget Office report, Availability and Use of the F/A-18E/F Super Hornet Fighter Aircraft.
From the report
Than for the Rest of the Department of the Navy’s Fleet. Availability rates of Super Hornets
declined markedly between the mid-2000s and the mid-2010s; the older F/A-18C/D Hornets
experienced a longer and steeper drop. Both types of Hornets experienced...
https://news.usni.org/2023/02/10/cbo-report-on-super-hornet-availability