The Variance Learning Curve

38 Pages Posted: 17 Jul 2020

See all articles by Hessam Bavafa

Hessam Bavafa

University of Wisconsin - Madison - School of Business

Jónas Oddur Jónasson

MIT Sloan School of Management

Date Written: June 25, 2020


The expansive learning curve literature in Operations Management has established how various facets of prior experience improve average performance. In this paper, we explore how increased cumulative experience affects performance variability, or consistency. We use a two-stage estimation method of a heteroskedastic learning curve model to examine the relationship between experience and performance variability among paramedics at the London Ambulance Service. We find that for paramedics with lower experience, an increase in experience of 500 jobs reduces the variance of task completion time by 8.7%, in addition to improving average completion times by 2.7%. Similar to prior results on the average learning curve, we find a diminishing impact of additional experience on the variance learning curve. We provide an evidence base for how to model the learning benefits of cumulative experience on performance in service systems. Our findings imply that the benefits of learning are substantially underestimated if the consistency effect is ignored. Specifically, our estimates indicate that queue lengths (or wait times) might be overestimated by as much as 4% by ignoring the impact of the variance learning curve in service systems. Furthermore, our results suggest that previously established drivers of productivity should
be revisited to examine how they affect consistency, in addition to average performance.

Keywords: Learning Curves, Performance Consistency, Service Time Variability, Operational Performance, Service Operations, Ambulance Operations

Suggested Citation

Bavafa, Hessam and Jónasson, Jónas Oddur, The Variance Learning Curve (June 25, 2020). Available at SSRN: or

Hessam Bavafa

University of Wisconsin - Madison - School of Business ( email )

975 University Ave
4284C Grainger Hall
Madison, WI 53706
United States

HOME PAGE: http://

Jónas Oddur Jónasson (Contact Author)

MIT Sloan School of Management ( email )

100 Main Street
Cambridge, MA 02142
United States

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