The middle-aged bubble does not only pertain to the baby boomer generation. Wisconsin forests are experiencing this age phenomenon as well.  Wisconsin forest data shows a significant bubble of acreage in the middle age class (60-80 years old) with lesser amounts in the very young and very old age classes. This middle age bubble can be attributed in part to the cutover period when many of these forests originated.

Total acreage of timberland between 1983 and 2017 distributed by stand age class. Error bars represent the 68% confidence interval. Source: Forest Inventory and Analysis, 2017.