While I mostly agree with your statement there's evidence that testosterone is linked to social status and mental well being.

A 50% drop most likely has a multifactorial explanation, being told that some traditional male traits are bad (and thus lower well being or social status) or medicated away (see e.g the rise in ADHD and Autism diagnosis) might have some effect.

I'm not nearly knowledgable enough to give any reasonable estimate but it would not surprise me if it was higher than 0%.