Thanks for following up. I say what I do in part because I know in my own diocese the number of people they get (or have gotten in the past) petitioning for admission consecrated eremitical life under c 603 is many times the number of c 603 hermits we have (a ratio of about 120 to 1). I also belong to a couple of groups of hermits online, the majority of members of which are lay or non-canonical. The membership of one of these groups is more than 300 -- though I would guess about half are just curious about hermits or maybe "wannabes". Even so, that leaves @150 lay or non-canonical hermits in the group. The second one is drawn from Catholics and I am not sure of the number of members, but several hundred -- only a handful of which are canonical. The first group mentioned above then, are from a single diocese in this country, and the second group is drawn from many dioceses from more than one country. That alone suggests to me that there are far more lay hermits out there throughout the world than there are consecrated hermits and that the numbers will remain that way for the foreseeable future.
Partly my guess in this comes from the rarity of consecrated diocesan hermit vocations. Dioceses, rightly I think, don't profess everyone who comes in the door seeking to be professed. There are many reasons for this. Most are valid while some few are not. Many of those refused admission to profession will continue to live as hermits in the non-canonical state; it is what God calls the person to be. Some of these will re-petition in several more years, after living the life and gaining the experience needed to live this vocation in the name of the Church; they may be granted admission to profession at that time; others will remain lay or non-canonical hermits for the rest of their lives --- that is, they will be hermits living this life by virtue of their baptism and standing in the baptized (lay) state, without admission to a second consecration (or to standing in the consecrated state) as the language goes today.
I also know because I hear from non-canonical hermits mainly in the US and Great Britain or, because I see the numbers of non-canonical hermits from all over contributing to publications like Raven's Bread. Some dioceses don't profess c 603 hermits, but they do allow non-canonical hermits to commit or dedicate themselves at Mass (Archdiocese of Seattle is one of these and may be a pioneer in this arrangement). Regina Kreger, whom I've written about in the past is a non-canonical hermit who writes some beautiful reflections. Joyful Hermit, with whom I have mainly disagreed over the years, is also a known dedicated lay hermit with private vows and a significant online presence. For every canonical hermit I meet or hear of, I meet or hear about several, even many, others who are non-canonical. Thus, I believe there are more lay or non-canonical hermits out there than canonical ones --- and after all, that is how it has always been, particularly since the days of the Desert Abbas and Ammas!!Finally, because I know eremitical life to be a significant and prophetic vocation that militates against the individualism epidemic in our time and speaks in a particularly vivid way to the chronically ill, disabled, or those who are otherwise marginalized, I believe that God calls people to it in real numbers and in every state of life (except marriage). A tiny minority of these are c 603 hermits, and that is as it should be. There "must" be a greater number of lay hermits, not least because the lay state is so critical for the healthy and vibrant life of the church, but also because rare as hermits are, the vocation is radically Christian and every state needs the modeling hermits provide! It is a rare and focused vocation, but it is not meant to be an esoteric or an elitist one!! This is one reason I was very pleased to hear what the Archdiocese of Seattle is doing with lay hermits there! When I answered your original question, I remarked on the appropriateness of God calling people to be hermits in lay, consecrated, and clerical states. I definitely find that fact both inspiring and humbling! Those c 603 hermits I know personally, feel similarly.
Postscript (04 October): please note that non-canonical does not mean illegal or that one is an illegal hermit!!! No one baptized as a member of the Church is illegal!! Non-canonical is a shorthand way of saying that one is not bound by additional canon laws beyond those that come with baptism. This is especially the case when there is the possibility of canonical solitary hermits. When a person becomes a c 603 hermit, new canons (norms) apply to them that did not apply simply because they were baptized. When a person becomes a religious or priest, new canons apply to their life that did not apply to them in their baptismal state alone. The same is true of hermits now under c 603. These persons have been granted and embraced rights and obligations a person does not have by virtue of baptism and the other Sacraments of initiation alone.