  The normalized probability density function (PDF) of global measures of a
large class of highly correlated systems has previously been demonstrated to
fall on a single non-Gaussian "universal" curve. We derive the functional form
of the "global" PDF in terms of the "source" PDF of the individual events in
the system. A single parameter distinguishes the global PDF and is related to
the exponent of the source PDF. When normalized, the global PDF is shown to be
insensitive to this parameter and importantly we obtain the previously
demonstrated "universality" from an uncorrelated Gaussian source PDF. The
second and third moments of the global PDF are more sensitive, providing a
powerful tool to probe the degree of complexity of physical systems.
