Popularity rating numbers indicate how many baby girls or boys per thousand were given that first name. For example, a popularity rating of 1.0 indicates that one of every thousand girls or boys born was given that first name. Although it doesn’t sound like much, a name with a frequency of one per thousand is a fairly popular name. 

Similarly, a popularity rating of .10 indicates that one of every 10,000 baby girls or boys was given that name, and a popularity rating of .01 indicates that one of every 100,000 baby girls or boys was given that first name. In Part 3, Popular and Unusual Names with Popularity Ratings, names which do not have a popularity rating indicated are rare names with a frequency of less than one in 100,000. Often these names are one in a million, such as Rylicia or Dollarian.