The initial screen is grayed out, and tells the user to click on any county. The user can also enter a county or major city via prompt. On the top right of the map there is a Year selection from 2005 to 2010.
When you select the first county, two colors on the county will populate, and line colors. The red counties mean they took more migration than they sent out, and blue counties mean they sent more migration than they took. The counties are also having different shades/ opacity of red or blue depending on how many migrated in or out.
The second image is a selection without the lines, this is easier to see has the lines overlaps the map near the selected county It can been seen that there are more red counties then blue, but its hard to pinpoint by how much the difference is between outbound and inbound.
The year bar graph does more justice to the interactive; it shows if the county has more people coming in or going out, also how it is doing in the following years. You can see that there is more outbound starting at year 2005, and is decreasing has the year passes. The barchart is dynamic per county selection.
The application has more information for colored county by hovering after you selecting the county. For this example I picked a small county (Koochiching County, Minn) that has very few migration. You can see how many people migrated to and from, and income per capita. This shows if there is a difference in capita when migrating