Using TheillDSim test if the between region inequality is significantly different from what would be expected under a spatially random allocation of county incomes across the US. I have a geodata frame named combined_data1, it has a column named 2021 which represents the per capita income. I am only focusing on 2021. The geodata frame has a column name combined_region which represents the region of the counties. The combined_region has 4 options Northwest, Southwest, Northeast, and Northwest.