Minority shareholders receive a discount for lack of control based on the value of control benefits they cannot take advantage of. For example, taking an active stance in management decisions, influencing the board of directors, paying shareholder dividends, liquidating company assets, and more.
Any benefit that constitutes a form of control that such shareholders cannot leverage is factored into the overall discount applied to the share price they are presented with.
To determine what the discount for lack of control will be, all manner of conditions and empirical studies may be assessed. The exact result differs by the methods used to obtain it and the status of the company.
A company being public or private can also influence the discount for lack of control greatly.
Applied in reverse, an empirical study can be used to specify a higher price for controlling stake in a company than its non-controlling shares were trading for on the open market, setting an implied discount for lack of control in the process.