Updated: Oct 13, 2018
It's based on U.S. Census Bureau data. The blog post also includes some good info on the pros and cons of different siding types.
Siding use differs radically by region. Up here in Minnesota, both brick and stucco would play a much smaller role in home design today. No doubt stucco would dominate if it was based on data from Arizona. Too bad the chart doesn't show that level of detail!