Returns \(\lifedisp_x\) the life disparity at Age \(x\) given by the integral \begin{equation} \lifedisp_x=-\int_x^\infty \frac{\sfrac(a)}{\sfrac(x)}\log\left(\frac{\sfrac(a)}{\sfrac(x)}\right)da . \end{equation} If Age is not specified it defaults to 0. Epsilon specifies the accuracy of the numerical integral. If not specified it defaults to Epsilon=1.0e-6.