Obtaining numbers for events past present and future is no easy task. Honbu organizes the big events in Japan but the national and non-Japanese International events are organized by other groups. Personally I am not going to contact Honbu and ask for what information they may have primarily since I would have to give a reason beyond I would like to know. I ask quite a bit from these people and I would like to limit the number of e-mails they get from someone as low on the totem pole as I am. There are people there already preparing for my trip. Perhaps while I am in Japan I can ask for the information but as Karl pointed out it would serve no purpose. It wouldn't convince you to the value of competion in AIkido.
Secondly, why do you demand data. It should be enough that either Karl or I say it is the case. If we are dishonest we could feed you fake data and you wouldn't be the wiser. There are people who were at both Imabari, Australia and previous international events - if they say the numbers of people are increasing than it is - whether it is 10, 15 or 50% is immaterial. If they are confident enough to book an entire stadium for the big event in Osaka this October, that should say enough.
No one ever asked you to back up the statement that toshu randori never caught on with hard facts and from my perspective it is enough that those who experienced the events say differently. This is a casual forum - not a court of law.