Flowmap Blue is an open-source visualizer that maps out directional data organized in pairs. Using a MapBox API, "flows" (shipments of loaned and borrowed materials) are diagrammed between pairs of coordinates.
Yellow lines indicate transactions with university/academic libraries, green with public. A wider line indicates a higher volume of materials being shared. Whether a library has lent or borrowed more will determine what the tooltip will mention on mouseover - each library's point on the map will have more complete information.
Tip: Looking for a particular library? Use the search box in the top right to find it. Then, hover your mouse over its dot to see a detailed breakdown of its transactions.
MelCat is an online catalog service that allows patrons of participating libraries to borrow materials - books, movies, music, and more - from all over Michigan and have them delivered to their home library. This interactive map tracks the circulation of materials over the last 20 years to and from Wayne State University.
View a more detailed map, with options for filtering transactions down to the month, here.