No credible figure exists for Zhengyi Taoism, and the reason is instructive rather than merely inconvenient. Its priests are village and household ritual specialists, generally engaged for particular occasions by families and communities that would not describe themselves as members of anything, and there is no roll to count. This is the ordinary condition of Chinese popular religion, which the categories used by census-takers fit badly.
The tradition is strongest where the twentieth century interfered least. Taiwan has an unbroken and highly developed liturgical practice, and the Celestial Master lineage transplanted there in 1949 gave it institutional weight. Hong Kong, Singapore, Malaysia and the wider Chinese diaspora sustain temples and ritual specialists. In the People's Republic, temples were closed and priests dispersed during the Cultural Revolution, and the tradition has been rebuilt since the 1980s within the framework the state provides.
What survives most robustly is the ritual itself. The jiao offering, the funeral liturgies, the talismanic healing and the temple festivals are woven into the ordinary life of Chinese communities, and much of what an outside observer would call folk religion is served by Zhengyi priests using texts and forms of considerable antiquity. Scholars working in Taiwan and Fujian from the 1960s onward found liturgies in living use that they had previously known only from the medieval canon.
The tradition's own view of itself is worth noting. It presents less as one option among several than as a service performed for the community by those qualified to perform it, which is why the question of how many Zhengyi Taoists there are is, in its own terms, slightly beside the point.