Where Will You be Living in a Few Years?
This past week, I came across a rather interesting article published by the New York Times. The article charts the migration and diaspora patterns of people living in the United States since 1900, using US Census microdata. It goes state by state, showing two sets of data on two different charts for each state. The first chart takes the people residing in that state, and breaks down where the residents were born, by percentages. The second chart takes the people born in that state, and breaks down where they move to, also by percentages. A companion to these charts was released as well, visualizing the data on top of a map of the US. Each state is cut up onto parts of varying sizes, with each part representing a state, and the size of the part indicating the the percentage of residents that were born in the corresponding state. The companion charts this data across the years 1900, 1950, and 2012. This article tells an interesting story for each individual states. However, these states are never totally independent. Each state relies on the states around them. So, then, what do these individual migration patterns tell us in context of the entire nation? How can we identify these culturally, socially, and economically similar regions? Where should we focus our regional development efforts to best reach the citizens?
Fortunately, the charts are not the only way to visualize this data. We can re-imagine it all as one big, directed, weighted network, with each state being a node, and each edge being movement out of a state. We will use the percentage outflow as the weights, making sure to ignore insignificant (say, less than 1%) links. This network offers us a much better understanding of the affinities between states. From this network, we can identify states that satisfy the Strong Triadic Closure principle that we learned in class. Montana is one such state – it has strong edges to both California and Washington. Under Strong Triadic Closure, we would expect an edge to exist between California and Washington – which is indeed the case. Washington sends 5% of people born there over to California. Of course, this is just one example – there are many more states across the country that also follow Strong Triadic Closure. Finding them allows us to better understand movement both within and between regions.
Since we have clear areas of dense and less dense connections, we can actually go ahead and partition the network (an optional technique discussed more in depth in the textbook). With some more data, such as any cultural, social, or economic factors present, researchers can provide some interesting conclusions. This combined analysis can even be extended to the county level, creating a hub and spoke network, which explains both inter and intrastate migration patterns. Aggregating these smaller networks up to a state, region, and even national scale reveals where the most influential social, economic, and cultural clusters are around the US. With this knowledge, legislators may even be able to direct policies to certain areas, allowing for efficient implementation.
Sources:
Companion Map: http://www.nytimes.com/2014/08/16/upshot/mapping-migration-in-the-united-states-since-1900.html?abt=0002&abg=0