Your first graph clearly shows lack of scientific rigor in data analysis. Regressing a linear line through that graph demonstrates that the person who did it isn't even qualified to be a statisticians bum hole.
At best the graph illustrates a step up change occurred half way along (199/2000?). If you were to regress the graph for pre 2000 you would get a nearly flat line below the axis. If you were to regress the graph post 2000 you would get a nearly flat line above the axis. You can do it visually by covering the respective halves of the graph and observing.
