I would like to update my estimate above.
It appears that at least 5 million people worldwide have PFS. A study by Prof. Belknap shows that adverse effects reporting in clinical trials of finasteride was inadequate. Prof. Traish agrees saying that “level of harm is tampered down significantly”. He estimates prevalence of persistent side effects at 3-5%. In his latest paper, he writes:
“[A]pproximately 30 million young men, worldwide, would be prescribed finasteride or dutasteride to treat male pattern hair loss. Even if the incidence of persistent sexual adverse events is 3% to 5%, which may be viewed as a small number, approximately 900,000 to 1.6 million men would suffer persistent sexual and psychiatric adverse events.”
https://www.sciencedirect.com/science/article/pii/S0015028219325993
These are the numbers only from finasteride and dutasteride for hair loss. The number of people who take these drugs for benign prostate hyperplasia is much higher, plus the dose is higher as well. As a result we can expect a lot more PFS cases. The conservative estimate is 3 million for both indications.
On top of that we have millions of people worldwide taking Saw Palmetto for a lot of different indications. The herb is extremely popular in many countries around the world, is advertised heavily, has a much wider reach than prescription drugs, and is completely unregulated. I know 2 people who got PFS from Saw Palmetto.
It is reasonable to assume a comparative but slightly smaller number of people have gotten PFS from Saw Palmetto as from Propecia and Proscar combined, as risk would be lower but use may be higher. Perhaps 2 million is a good estimate.
That brings the total number of people with PFS to 5 million.