Table 1.

Variables considered for inclusion in the econometric model.

Education data

  • Percent of people over 25 with a high school degree

  • Percent of people over 25 with a bachelor’s degree or higher

  • Elementary and secondary school enrollment

  • Average state SAT scores

  • Percent enrollment in high school

  • Number of degree granting institutions and branches

  • Average pupil/teacher ratio in elementary schools


Economic data

  • Gross state product

  • Average per capita income

  • Disposable income per capita

  • Average household income

  • Total state government revenue

  • Total state government expenses

  • Percent of state government expenditures on natural resources


Demographic and other data

  • Percent of urban land

  • Percent of urban population

  • Race (percent minority)

  • Sex (percent male)

  • Number of ISA Certified Arborists in the state

  • Region (South, Northeast, Midwest, and so on)

  • Number of certified Tree City USA communitiesz

  • ↵z Tree City USA is sponsored by National Arbor Day in cooperation with the USDA Forest Service and the National Association of State Foresters. This certification is a means of providing direction, technical assistance, public attention, and national recognition for urban and community forestry programs (The National Arbor Day Foundation 2006).