The sacred plaques of Jingū at Ise, officially called Jingū Taima, are distributed through jinja across Japan, with most of the activity happening at the end of the year. Almost any staffed jinja will have Jingū Taima available if you ask at the office, and, particularly in more rural areas, it is common for the priests and other people closely connected to the jinja to go door to door around the area, asking people if they want a Jingū Taima.
The distribution of Jingū Taima is a really big issue for Jinja Honchō. Indeed, it may be the biggest issue. According to Jinja Honchō, every kamidana should have a Jingū Taima on it, and every household should have a kamidana, so there should be one Jingū Taima for every household in Japan. This is far from being the case, although somewhere in the region of nine million of the plaques are distributed every year (one of them to me). For the last several decades, Jinja Honchō has been trying, and failing, to increase the number distributed. Even the recent jinja boom has not helped, and although lots of women in their twenties and thirties are visiting jinja, that demographic has one of the lowest levels of Jingū Taima ownership.
Jinja Shinpō is filled with articles about the importance of distributing Jingū Taima, exhorting priests to do everything they can to increase the number they distribute, and to educate both priests and the people who live near the jinja in the significance of the plaques.
The problem is that, after reading Jinja Shinpō cover to cover every week for about five years, and reading all the literature that Jinja Honchō distributes about Jingū Taima, I am still unclear as to what, exactly, the significance of the plaques is supposed to be.
As sacred plaques for Jingū, they are formally vessels for the spirit of Amaterasu Ōmikami, so that the kami would be present on the kamidana. Jinja Honchō is not even explicit about this, although that could be because they take it to be too obvious to state. If we grant this religious meaning of the plaque, then the meaning of Jinja Honchō’s position is that every household should honour Amaterasu Ōmikami on their kamidana.
One could speculate that the reason why they do not make this explicit is that it would be very hard to convince every household in Japan, or maybe even the ten million that has been the target for decades now, to take in a Jingū Taima. Far too many people would simply fail to believe it. With some people, it may be better to take the approach of simply saying that it is a Japanese tradition, and one that they should maintain. That certainly has some truth to it; possession of a Jingū Taima was extremely common in pre-modern Japan. (In pre-war Japan, it was almost universal, but it seems that it was almost de facto compulsory.)
The problem is that this leaves Jinja Honchō without a clear answer to the question “why should I have one of these?”, and that is going to make it very difficult to get new people to start venerating them on their kamidana.
If I had to point to the biggest problem in Jinja Honchō’s current practice, it would be this. This is their central activity, and they have no clear, public answer to the question of why they are doing it. I cannot imagine that they will see any increase in the number of Jingū Taima distributed until they resolve this problem, one way or another.