http://www.adherents.com/Religions_By_Adherents.html#Shinto
Shinto: Shinto is one of the “classic” eleven or twelve “major world religions.” But adherent counts for this religion are problematic and often misunderstood. In a nutshell, Shinto is simply the indigenous ethnic practice of Japan and its importance is almost entirely historical and cultural, not contemporary. The number of adherents of Shinto are often reported as being around 100 million, or around 75 to 90% of the Japanese population. These figures come from the Shukyo Nenkan (Religions Yearbook), put out by the Ministry of Education & Bureau of Statistics, and they obtain their figures by asking religious bodies for statistics. The Shinto religious bodies have on record most Japanese citizens because of laws established in the 17th Century which required registration with the Shinto shrines. Essentially everybody within local “shrine districts” were counted as adherents. This is comparable to certain Catholic and Protestant nations in Europe where the majority of people have been Christianed [christened? baptized?-Enda80] or otherwise counted as a member of the state church, but where large proportions of the population are non-practicing.
The difference is that in those European countries, those people are at least nominally adherents of the religion that claims them. “Nominally” here means if asked their religion, they can recall the name of the church they were baptized into as an infant, and don’t mind citing that as their religious preference. In Japan, the majority of adherents of Shinto, as claimed by the Shinto organizations, don’t even consider themselves adherents, even nominally. In polls, only about 3.3% of the Japanese people give Shinto as their religion. A high world-wide figure for people who consider themselves primarily practitioners of Shinto would be about 4 million. Certainly most Japanese people participate in holidays which have Shinto roots, but in this list we are trying to track self-identification, not general vestigial influence. Also, the strongest active religions which have Shinto roots (such as Tenrikyo) no longer claim to be “branches” of Shinto, and can be listed separately.