agency vs area of authority

agency

noun
  • The office or function of an agent; also, the relationship between a principal and that person's agent. 

  • A medium through which power is exerted or an end is achieved. 

  • A department or other administrative unit of a government; also, the office or headquarters of, or the district administered by such unit of government. 

  • The capacity, condition, or state of acting or of exerting power. 

  • An establishment engaged in doing business for another; also, the place of business or the district of such an agency. 

  • The capacity of individuals to act independently and to make their own free choices. 

area of authority

noun
  • the extent of someone's expertise, authority, activity or knowledge 

How often have the words agency and area of authority occurred in a corpus of books? (source: Google Ngram Viewer )