ABSTRACT
A Time-Based Learning Curve is an empirical relationship which reflects that the time, effort or cost to produce an output from an activity decreases as the elapsed time since commencement of that activity increases. Bevis-Towill Time-Constant model first appeared on the estimating landscape in the 1970s when research showed that in some situations time is a better predictor of learning than simply the cumulative number of units or repetitions. This model considers the output or yield per time period from an activity rather than the time or cost to produce a unit, but inherently one implies the other, as the average unit time per time period is simply the reciprocal of the output per period. The model assumes an initial starting level of output, after which output increases due to learning before flattening out asymptotically to a steady state level.
