I doubt that anyone can provide an accurate figure for Scientology's membership worldwide (churches and orgs in at least thirty countries). Such is the constant ebb and flow in and, I believe it's accurate to state, especially out of the group, it is unlikely that the organization itself has any idea of what its membership is on any given day. In my opinion membership has waned since about 1970. Scientology has had stiff competition from other cults, modern religions, New Age groups. Many of its staunchest members have left, and ever more of the raw public are reluctant to become involved. Among the reasons for this reluctance are:
an enormous increase in prices starting in the '80s, as always payment in advance;
written and televised exposes of enormities and harassment perpetrated by Scientology/Scientologists;
conviction of nine top-ranking Scientologists, including Hubbard's wife, of theft of government documents, and other crimes;
the Church's policy of nuisance lawsuits against its critics, including authors and their publishers;
published, verbal and Internet accounts of black-magic-like processes;
Hubbard's reported wealth and power, physical and mental ill health and mysterious death;
the sometimes obnoxious on-the-street confrontation of Scientology proselytizers;
leading Scientologists' poor showing in TV and radio debate with wogs;
the struggle on the Internet between Scientology and its detractors, the latter often using satire, a strong tactic against authoritarianism;
the speech mannerisms and zombie-like wide-eyed stare of some Scientologists, which may create the impression that something sinister is going on behind org walls.
But Scientology keeps rolling. If their membership is down, still they have managed to find more affluent people, on the principle that you may enlist either one thousand people who pay $1,000 each or, just as good, one hundred people who pay $10,000 each or ten people who pay $100,000 each.
Scientology has scored points with the media with their "Celebrity Center," which hosts famous entertainers and sports stars in the group.
And most importantly, Scientology was awarded a favorable decision as a non-profit organization in United States Tax Court, and can now legally call themselves a religion in this country. However, there have been strictures against Scientology in several other countries.