暴走族、初めて１万人割る 2010年警察庁まとめ the number of bike gang no. in Japan below 10,000 first time

http://www.nikkei.com/news/category/article/g=96958A9C93819695E2EBE2E1988DE3E2E2E0E0E2E3E3E2E2E2E2E2E2;at=ALL

暴走族の組織が不明確になってきていることを理由としてあげていますが、私は少子化の自然な流れかなとみてます。国民の中で暴走族が何パーセントいるかを過去にさかのぼって見ると面白いとおもいますよ。
The article said it is more and more difficult to define the bike gang group in Japan as one reason but I think the small child demography in Japan has the most significant impact. it could be interesting to see the percentage for the bike gang number against the total population in Japan and see if there is any change over the years.