I'm going to assume you mean "academy" attrition for sake of conversation.

You have a wave of much higher attrition after 2013 because....You have a lot more trainees on fewer trainers.

That means more load is placed on fewer trainers resulting on page 45 where you spike from 20% to 25% ratio.

Combine that with the very valid point that this is not CIT folks but qualifying citizens being admitted, you can see the impact of having a 56% higher attrition rate!

Here's a bunch of plans to comb through for the full numbers. I don't have a spreadsheet off hand.

https://www.faa.gov/air_traffic/publications/controller_staf...

https://www.faa.gov/sites/faa.gov/files/2021-11/FAA-Controll...

https://www.faa.gov/air_traffic/publications/controller_staf...

Alas - my key point is this: the statement

> Has this had a long-term impact on aviation safety and air traffic controller shortages? Likely yes."

may have been highly attributable in 2018 timeframe but the real culprit is just as likely the 2013 sequester - I'd caution to say any one cause is the reason but rather there is a combination between a shift in applicant pool, having to deal with a slight burst in retirements, recovering from sequester and revamped training processes. Heck - maybe even not having an administrator from 2017-2018 might have caused issues.

In the cold light of 2025 with impacts from COVID still reverberating, I'd doubt hiring practices as much as any other arbitrary reason.