Geological differences among various coalfields restrain the applicability of subsidence prediction using empirical approaches previously developed. The Bureau of Mines assessed data collected from 16 longwall panels in the northern Appalachian Basin. Attention was focused on the effects of rock lithology, excavation width, and panel depth on the subsidence factor. The results show that the subsidence factor can be expressed in terms of the width-to- depth ratio by a simple exponential equation, which has a coefficient tentatively considered as the subsidence index. This index varies with the lithology of a particular site, and can be expressed in terms of percent distribution of weak and strong rocks in the overburden.