Decay of a justified graph is expressed by the function of depth decay, meaning the sum of the reciprocal of depth from the root node to each destination, where the depth can be weighted by a power function.
Decay, of a justified graph
Dalton, R. C. & Dalton, N. S. (2007) Applying Depth Decay Functions to Apace Syntax Network Graphs. Proceedings of 6th International Space Syntax Symposium, Istanbul. Pp.089-01-14