  Problems in econometrics, insurance, reliability engineering, and statistics
quite often rely on the assumption that certain functions are non-decreasing.
To satisfy this requirement, researchers frequently model the underlying
phenomena using parametric and semi-parametric families of functions, thus
effectively specifying the required shapes of the functions. To tackle these
problems in a non-parametric way, in this paper we suggest indices for
measuring the lack of monotonicity in functions. We investigate properties of
the indices and also offer a convenient computational technique for practical
use.
