Overlap coefficient

The overlap coefficient, or Szymkiewicz–Simpson coefficient,  is a similarity measure that measures the overlap between two finite sets. It is related to the Jaccard index and is defined as the size of the intersection divided by the size of the smaller of two sets:


 * $$\operatorname{overlap}(A,B) = \frac{| A \cap B | }{\min(|A|,|B|)}$$

Note that $$0 \leq \operatorname{overlap}(A,B) \leq 1$$. If set A is a subset of B or the converse, then the overlap coefficient is equal to 1.