Final answer:
The Air Force has experienced the greatest percentage of growth since 1950.
Step-by-step explanation:
The group in the American forces that has experienced the greatest percentage of growth since 1950 is the Air Force.
The Air Force underwent significant expansion during the Cold War and has continued to grow since then.
For example, in 1947, the Air Force was established as an independent branch of the military, separate from the Army. This allowed it to focus on its own growth and development, leading to its significant expansion in the following decades.