States and Passports

Not only does this site have an interactive map to look at the level of passport holders in each state, but if has this great graph which lends itself nicely to a line of best fit.

I can display this graph and ask, "how many passports will be given out in 2014?" Or I can blur out a point or two and see how close they can get to the actual numbers. So I could blur out 2013 and see how the actual numbers compare to their predictions.