The figure is based on research about how workers at comparable positions at other companies are paid; it doesn't take into account the candidate's salary history or other personal factors. (inc.com)
Most professionals do a formal or an informal assessment of salary levels for comparable positions when they are considering several job offers. (topresume.com)
Then you can simply look into comparable field of work and into other sectors and locations that may offer comparable positions. (cpolemployment.com)