  We consider the contextual fraction as a quantitative measure of
contextuality of empirical models, i.e. tables of probabilities of measurement
outcomes in an experimental scenario. It provides a general way to compare the
degree of contextuality across measurement scenarios; it bears a precise
relationship to violations of Bell inequalities; its value, and a witnessing
inequality, can be computed using linear programming; it is monotone with
respect to the "free" operations of a resource theory for contextuality; and it
measures quantifiable advantages in informatic tasks, such as games and a form
of measurement based quantum computing.
