learning curve 
noun
The rate of a person’s progress in gaining experience or new skills: the latest software packages have a steep learning curve...
- The heuristic concept of learning curves describes cost reductions as a function of cumulative production.
- Turf wars and learning curves influence how new technology is adopted in hospitals.
- Plotting these production costs against units of production along a graph yields a learning curve that slopes from the upper left to the lower right.