This line graph sample shows the number of airlines departures in 1996-2002. It was designed on the base of the Wikimedia Commons file: -6 time series.JPG
[commons.wikimedia.org/wiki/File:-6_time_series.JPG].
"The social science of economics makes extensive use graphs to better illustrate the economic principles and trends it is attempting to explain. Those graphs have specific qualities that are not often found (or are not often found in such combinations) in other sciences. ...
More generally, there is usually some mathematical model underlying any given economic graph. For instance, the commonly used supply-and-demand graph has its underpinnings in general price theory — a highly mathematical discipline." [Economic graph. Wikipedia]
The line chart example "Number of airlines departures in the given years" was designed using the ConceptDraw PRO diagramming and vector drawing software extended with the Line Graphs solution from the Graphs and Charts area of ConceptDraw Solution Park.