There is only one official statistic is available, which is the number of those people who have allocated the 1% of their income tax on their tax filings to the Church of Scientology (until it was deregistered as a church and transformed into a religious  association in 2012):

According to the website of the Hungarian National Tax and Customs Office, :

Year         # of people     amount paid to the Church

2002:       840                     3 368 400 HUF
2003:       833                     3 568 192 HUF
2004:    1034                     4 109 757 HUF
2005:      880                      4 154 000 HUF
2006:    1263                     5 727 350 HUF
2007:    1138                     5 571 377 HUF
2008:    1062                     5 270 498 HUF
2009:    1161                     5 496 052 HUF
2010:    1219                     5 080 927 HUF

As a religious association (Note: This is a different kind of 1%, and Scientology shares this option with every non-profit organization in Hungary. Before 2011, they were able to ask for the other kind of 1%, which is restricted to registered churches only.):

Year         # of people           amount paid to Scientology

2011:     233                             789 100 HUF
2012:     436                         1 374 915 HUF
2013:     371                         1 023 100 HUF
2014:     281                             942 714 HUF
2015:     289                             971 670 HUF
2016:     343                         1 244 499 HUF

Hungarian Scientologists Going to the U.S.

The number of Hungarian Scientologist going to the US
to work for the C of S was 202 between 2009 and 2015, according to a FOIA request.