The given line graph illustrated the number of cases of X virus disease in Someland from 1960 to 1995.
Overall, the incidence of disease increased from 1960 to 1980, followed by a sharp decline between 1985 to 1990. By 1990, the disease had almost disappeared and remained at that low level until 1995.
In detail, the number of cases remained stable at around 100 between 1960 and 1965. After that, it was increased to 200 cases in 1970. The most dramatic increase occurred between 1970 and 1975, when the number of cases jumped from 200 to 500, and this position remained constant until 1980.
However, after 1980, the number of cases began to fall from 500 to 400 in 1985. The most dramatic falling happened between 1985 and 1990, when cases dropped to almost zero. From 1990 to 1995, the incidence of disease stayed extremely low.
