Spearman's footrule

Spearman's footrule is a way to compare two rankings or lists by measuring how different they are. Imagine lining up two lists of items and noting the position of each item in both lists. The footrule sums up the absolute differences in these positions for every item, giving a single number. A smaller sum indicates the rankings are very similar, while a larger sum shows more differences. It's a simple, intuitive way to quantify how much two rankings disagree, commonly used in statistics and data analysis to assess the similarity between different orders.