Link to application: http://gfdc.herokuapp.com/
Geni.com World Family Tree is a unique collaborative, largely public collection of connected family trees. The Geni Forest Density Calculator (GFDC) is designed to test the density of the forest surrounding a profile. The density at a particular profile node is calculated as the number of unique profile nodes within n steps of the node. All members of a node’s immediate family (parents, siblings, spouse/partner, and children) are defined as one step away from the node.
Please note that the GFDC may be limited by privacy settings or by anomalies in the Geni database.
Simply - number of people in your tree with the distance n from you (number of steps in the path)