In the United States, there are two certification organizations; the Board for Certification of Genealogists (BCG) and the International Commission for the Accreditation of Genealogists (ICAPGen). From a count of the list of genealogists on the BCG website, it appears that they have approximately certified 300 members. Making the same count on the ICAPGen website shows there are something over 200 accredited members. The ICAPGen list is complicated because there are individuals who are accredited in more than one area. From my past experience this does, indeed, show an increase in membership.
The real issue, however, is defining the term "professional" when used with genealogist. Am I a professional because I have been paid to "do genealogy" in the past. My flippant definition of a professional genealogist has been anyone who can spell both words, but that overlooks the tremendous effort put forth by those who are either certified or accredited. It would be very simple to limit the term professional to those two categories, but there are many very fine genealogists who do not seek either accreditation or certification. What about the membership of the Association of Professional Genealogists (APG)?
Membership in the APG is not necessarily an indication that the genealogist is actively seeking renumeration as a professional. Many of the members do not accept clients.
In short, it is very difficult to get a feel as to whether the number of professional genealogists is increasing, staying about the same, or even decreasing. If we go abroad and consider Great Britain, I find the following statement from the British Society of Genealogists:
The great growth in interest in genealogy and family history and the corresponding technological developments and online resources has seen a number of related career opportunities develop in the subject which scarcely existed twenty or even ten years ago. However there are still relatively few people making a full time living solely as genealogists tracing the family history of other people for a fee. Most people who call themselves genealogists often supplement any living they earn from research by writing, teaching or lecturing, looking for living people, transcribing and indexing records, maintaining databases, working in archives and libraries or practice their genealogy along with other jobs or sources of income or support.If you accept a very broad classification of "genealogist," you can probably make a case for a growth in the profession. But from my perspective, the number that make a reasonable living solely from "doing genealogy" is extremely small compared to practically any other profession.