The world population has grown significantly in the 20th century and is projected to grow exponentially in the 21st century mostly in the developing regions. This growth rate can be understood with a simple two-dimensional (2D) graph that shows the population growth as a funtion of time. The dashed line is a prediction based on available data that assumes finite resources, Ref [1].
A well designed graph, as shown here, can be a powerful tool to show a correlation or a possible relationship.
Last revised July 3, 1996
http://www.sv.vt.edu/class/surp/surp96/laughlin/stat/3D_tutor/world_pop.html