Edit: I can't seem to connect to the Japanese statistics page, but that too is sourced, and I can't imagine they'd just flat out lie about the contents of a publicly available document...
Thanks for the link. This statistic does not have a separate category for high speed trains and consequently cannot be used to make statements about them.
The relative drop in rail traffic is much more likely due to the fact that local short distance routes have been closed down aggressively in the past 20 years. In Germany, also medium speed trains routes (160km/h), like the ones serviced by the InterRegio, have been cut.
Using this statistic to make any claims about high speed trains is naive or intellectually dishonest.
http://ec.europa.eu/publications/booklets/eu_glance/44/en-3....
Look near the bottom of page 52...
Edit: I can't seem to connect to the Japanese statistics page, but that too is sourced, and I can't imagine they'd just flat out lie about the contents of a publicly available document...