In the 1980's and 1990's (until the mid-nineties anyway), I got used to nearly all of the trains, buses, and train station platforms being full of advertising (in the corners, on the doors, hanging in the aisles, etc.), and then as the economy steadily got worse after the collapse of the "bubble economy", I began noticing that much of the available advertising space out in the countryside was left blank, awaiting customers. I got used to the phenomenon of seeing fewer and fewer ads out on fringe branch lines and at branch line train stations away from the center of Tokyo, but through it all, the advertising space on the main lines within Tokyo was always full. Considering a company's viewpoint, it was easy to imagine that they wouldn't want to spend scarcer advertising money on ads that not many people see.
Back in the central area, the ad space being full on the Yamanote Line and the Chuo Line was comforting in a way - no matter how empty billboards and train advertising space was on the edges of the city, the center carried on looking as busy as ever. And so it's come as a shock recently to discover some empty advertising panels on the Chuo and Yamanote lines (not many, but they have always been completely full before...). Particularly on the Yamanote Line - you stand there on one of (if not the) most popular train lines in the world, and confronted with an empty advertising space, you can only conclude that the economy really is bad. It's as though you couldn't sell advertising for the Super Bowl or something. A space guaranteed vast numbers of viewers, and it goes empty for want of a renter?
The advertising spaces on the Yamanote Line and the Chuo Line are still generally full, but over a quarter century, I had never seen any empty space on them at all, so it seems significant. It's sort of like an advertisement saying "Welcome to Great Depression-II"....
Lyle (Hiroshi) Saxon