Why was one of the earliest project tracking devices referred to as an “S-curve?” Do you see value in the desire to link budget and schedule to view project performance?

This early device compared project time and cost graphically.  The nature of project time and costs creates an S when the points are plotted on a graph, hence the term “S-curve.”  There is value in linking the budget and schedule as an indicator of project performance.  Following the S-curve, managers can get a rough depiction of expected progress.  They can also see deviations of their own project from the typically expected progression.