# Rarity of versions

A very important consequence of the fact that the identification system introduced by the catalogue is based on the examination of more than 1300 different thalers is that rarity of the thaler versions can be estimated. The sample is considered large enough to provide a good basis for empirical estimation of the current occurrence frequencies. Let N denote the total number of thalers examined (cca. 1320) and let Ni denote the number of thalers of type "i" within the entire population. The * logarithmic rarity value* (Ri) of this type is defined as the entire part of the expression