a cross-section from 1972
number of observations : 30
observation : regional
country : United States
A dataframe containing :
indicator of air quality (the lower the better)
value added of companies (in thousands of dollars)
amount of rain (in inches)
is it a coastal area ?
population density (per square mile)
average income per head (in US dollars)
Verbeek, Marno (2004) A Guide to Modern Econometrics, John Wiley and Sons, chapter 4.