Objective : This visualization is mainly used for temporal data.
Application : Line graphs are used to display a quantitative value over a continuous interval or duration.
This chart is most often used to show trends and relationships. Linear graphs also help to provide a global view of a given interval, to see how it has developed over this period.
Limit to 3 lines to keep reading easy.
Shouting example with the evolution of the presence of women in different trades. Note that the only business that has been steadily declining since 1983 is IT.
For more informations on chart types.