People in Japan are still more likely to go to a physical store and rent a DVD than to stream entertainment, and I haven't seen any evidence that DVRs ever really caught on.
I wanted to sort of update this. I was incidentally doing some reading today and it just happened to go into two very relevant topics: a) DVR has finally started taking off in Japan in the past couple of years and b) the way Japanese media services report ratings, the numbers currently do not account at all for viewers who are watching programs in time-shifted fashion via DVR.
So if your kids want to sleep in and then watch Super Hero Time over a late brunch, there's simply no way for the ratings to account for these viewers. Given that, if Kyoryuger's toy sales are high, then the low ratings may not actually be as serious a problem as we've been assuming. TV Asahi would certainly have the DVR issue in mind if it's starting to impact ratings.
Was there a reason for the spike in toy sales for the Rider shows?
As far as I can tell, it's just that the modular collect-a-thon gimmicks like Gaia Memories and Medals went over really, really well with children. The Rider Belt toys since Decade, particularly the OOO Driver, have also sold crazy-well. Kyoryuger's battery gimmick seems modeled on this sort of gimmick, and from the early charts, it looks like it's also going over pretty well with kids. It'll be a long time before we have real sales figures, though.
I don't think so...because they measure it in percentages. So even if less children are born in Japan, we're still taking the percentage of that age group.
Remarkably, the ratings figures we get aren't specific to the target audience, but instead are combined ratings. It's literally the percentage of the total population that tuned in for that show. It's worth pointing out that American ratings aren't measured this way-- they're based on percentage of total TV viewers at that time, I believe. I also want to say the American formula has been adjusted to take time-shifted viewers into account.