As a cartographer, the display of spatial information is of great interest to me. I’ve been particularly intrigued by analysts who are able to convey complex geographic information without resorting to a map. Previously, I had done a round of some of the methods in the article, “Spatial Unmapped.”
Chris Walker, who runs the storytelling with data site, viznary, used data journalism to create a compelling graphic showing migration patterns among states in 2012. Using data from the U.S. Census American Community Survey (ACS), the interactive graphic was developed using D3.js. (more: making maps with D3).
When first loaded, the graphic seems a jumbled mess, much like someone dumped a bunch of colored cables together. Hovering your mouse over the graphic filters down the data into more understandable segments. The outer wheel is divided into five color-coded segments representing the Northeast, Southeast, Midwest, Southwest, and West regions of the United States. Each arc within those segments is assigned to a state in that region, with the width of the arc representing the proportionate among of migration to and from that state. The inner circle contains bands connecting state to state with the widths also indicating the volume of migration. The color of the band indicates which state is sending the most migrants to another state:
The color of each link is determined by the state that contributes the most migrants, so for example, the link between California and Texas is blue rather than orange, because California sent over 62,000 people to Texas, while Texas only sent about 43,000 people to California.
Hovering over a state’s arc lets you see if more people are leaving or migrating to that state. For example, hovering over Alaska shows only significant migration to two states: California and Florida with more than twice as many people leaving the state than moving in.
Only states that sent at least 10,000 migrants to another state were mapped, therefore the states of Vermont, Montana, and South Dakota did not make the cut in the graphic.
The style of the graphic makes it easy to explore migration patterns. Hover over an arc and a popup provides statistics on the overall number of people migrating to and from that state. Hover over a band and getting the state-to-state statistics.
Chris Walker provides a synopsis of his findings in his write-up about his interactive. To explore the graphic visit: Restless America: state-to-state migration in 2012.