The damages per construction spending and per transmission metrics normalize the number of damages accounting for factors most directly linked to levels of excavation activity. However, there are other less direct factors that can also influence the number of damages, such as weather, population and the density of infrastructure in an area. To fully understand the damage trends, CGA's statistical consultant performed regression analysis on three years of comparable data at the state and national level, incorporating such additional variables. This more advanced analysis controls for other potential influences on the damage rate. (Visit Appendix B for regression methodology.)
National-level regression used building permits to indicate construction activity. State-level regression explored spatial variation and revealed influential predictors:
- Real GDP as an indicator of economic activity
- Housing starts indicating construction volume
- Population density capturing infrastructure density
The regression analysis tested whether damage trend results were statistically different over time. The analysis took into consideration the factors outlined above and suggests that the increase in damages per spending and transmission is partially explained by other variables. However, evidence shows 2022 damages were higher than 2021, pointing to a continued rise in damages.