A typical juvenile delinquent group is motorcycle gangs, known as bosozoku, which cause disturbances and acts of violence, etc. Fig. 4-1-3-1 shows the trends in the membership and number of bosozoku in the last 10 years. Membership has decreased consistently, numbering 22,703 persons (a decline of 3.0% from the previous year) in 2001. Meanwhile, the number of bosozoku has been on an upward trend, rising to 1,167 (an increase of 0.2% from the previous year) in 2001. With respect to the size of bosozoku, the percentage of such gangs with 30 or more members fell from 13.7% in 1992 to 5.8% in 2001, indicating that these gangs are becoming smaller in scale (Source: Traffic Bureau, National Police Agency).

Fig. 4-1-3-1 Trends in membership and number of bosozoku (motorcycle gangs) (1992-2001)