The determination of the number of businesses operating in Arizona is not a straightforward proposition due to data deficiencies and definitional issues. The best data — from the U.S. Census Bureau — are more than two years old. The Census Bureau data are divided into two series: businesses with employees and nonemployer businesses. Each series is based on administrative records. While neither series is affected by sampling error, both are subject to nonsampling error. Certain industries are excluded from each series.

The demand for new workers in STEM (science, technology, engineering and mathematics) occupations in Arizona is a function of net job growth in these occupations in the state and the number of workers leaving STEM jobs in Arizona. Employees may leave their position for various reasons, including to retire, to move out of the state, or to change their profession. The supply of new workers in STEM occupations in Arizona is a function of the number of new college graduates in related majors, the number of workers moving to the state who are qualified to fill STEM jobs, and the number of Arizonans who are qualified to fill STEM jobs moving from a non-STEM to STEM occupation.