That is a pretty heinous drop so much so I referenced the global sales figures. I was shocked that it has gone unnoticed, but the console market in Japan according to this sites figures accounts for only twelve percent of the worlds console market. Last year I did a similar analysis, and it accounted for sixteen percent. Hell this week the market accounted according to these numbers for eight percent of global console sales.
Were these trends to persist it is very likely that Japan will constitute less then ten percent of the global market in a few months. That is really insane when you think about it. The only bright side is the 360 is increasing year over year.