From Wikipedia:

"In June 2018, four political activists known through social media – Paul Joseph Watson, Mark Meechan, Carl Benjamin, and Milo Yiannopoulos – joined the party. This was followed by the party gaining around five hundred members.

In July 2018, it was reported the party had attracted 3,200 new members, a 15% increase. However, this was a short-term gain as later research showed that UKIP membership in 2019 had declined to around 26,000."

Minus 26,000. Ouch. Thanks, Sargnome.