The more diverse the Tor network, the harder it is to track a connection. Currently there are a large number of nodes in North America and Europe. As of 2014, there is not enough coverage of the Tor network to perform circuit analysis. Even though it's good enough, the Five Eyes only get more eyes. Diversity needs to spread even more, primarily in Asia, South America, Africa, and Oceania.
This software is probably not perfect. It is a good reference but is not suitable for human judgement. Some of these countries do not run Tor nodes for good reasons, weather it is political or technological.
This page is nowhere near complete. Please see the TODO in the git repository.