 is a bit like the game where you have to change one word into another in a given number of steps by changing one letter at a time (the words in between have to be valid words). When the vocabulary is bigger this becomes easier. Therefore, the optimal threshold depends on the number of actual town names and the number of misspellings.</p>
<p>We have the official names and can therefore measure how many errors we make. We make an error when we put two records from <code>x</code> in the same group while they 