A "sphere of influence" is a plan for the probable ultimate physical boundaries and service area of a local governmental agency, as determined by LAFCo. The commission must also periodically review and update each plan. Factors the commission must consider in determining the sphere of influence of each governmental agency are: 

• The maximum possible service area of the agency is based upon present and possible service capabilities of the agency.
• The range of services the agency is providing or could provide.
• The projected future population growth of the area.
• The type of development occurring or planned for the area, including, but not limited to, residential, commercial, and industrial development.
• The present and probable future service needs of the area.
• Local governmental agencies presently providing services to such area and the present level, range and adequacy of services provided by such existing local governmental agencies.
• The existence of social and economic interdependence and interaction between the areas within the boundaries of a local governmental agency and the area which surrounds it and which could be considered within the agency's sphere of influence. 
• The existence of agricultural preserves in the area which could be considered within the agency's sphere of influence and the effect on maintaining the physical and economic integrity of such preserves in the event that such preserves are within a sphere of influence of a local governmental agency.