Referring to this article ( How well do vacuum constriction devices work ( on erectile dysfunction)) at the authoritative webmd.com.

Studies suggest that about 50%-80% of men are satisfied with the results of VCDs. As with any other method of treatment for erectile dysfunction (ED), satisfaction rates may decrease with time.

The article doesn't cite any study or reference. Is the 50-80% statistic believable?

The authoritative WebMD site has an article Erectile Dysfunction: Vacuum Constriction Devices:

A vacuum constriction device (VCD) is an external pump with a band on it that a man with erectile dysfunction can use to get and maintain an erection.

[...]

Studies suggest that about 50%-80% of men are satisfied with the results of VCDs. As with any other method of treatment for erectile dysfunction (ED), satisfaction rates may decrease with time.

The article doesn't cite any study or reference. Is the 50-80% statistic accurate?