We believe this plot depicts a real trend. However, the data certainly contain a bias in that recent
PhDs are more likely to be included in the tree.
An exponential model fit to this data suggests there will be 519 new PhysAnth PhDs per year by 2050.
Considering only the years 2000-2013, the relationship looks more linear. An OLS regression predicts 210 new PhDs per year by 2050.