The line graph illustrates how many reported cases caused by X disease in Someland over a 35-year period from 1960 to 1995.
Generally speaking, it is obvious that the number of cases of the infection increased dramatically until mid-seventies, followed by a sharp decline then completely disappear. The trend highlighted considerable fluctuations over the period shown.
In 1960, the numbers of cases were slightly above 100, and this figure remained stable until 1965. However, the disease began to spread rapidly in the following years, with the number of patients doubling to roughly 200 in the year of 1970 and reaching the peak at 500 in 1975. The quantity then stabilized steadily until 1980.
From 1980 onwards, the incidence of X disease took a downward trend, falling to around 200 cases by 1985. The decline continued rapidly and no reported cases were recognized in 1990. The number of people suffered by X disease has been zero between 1990 and 1995 and Someland was free from the illness.