Due to the increasing number of authors per publication, a change in counting method for a publication or citation indicator will often change the result of the indicator. Therefore it is important to know why a specific counting method has been applied. I have analyzed arguments for counting methods in a sample of 13 recent bibliometric studies and compared the result with discussions of arguments for counting methods in three older studies. Based on the arguments in the studies I formed argument categories which were grouped based on the underlying logics of the arguments. It resulted in four groups which can be used to describe and discuss how bibliometric studies with publication and citation indicators argue for counting methods. The first group focuses on arguments related to what an indicator measures, the next group on avoiding double counting of publications and/or citations, the third on pragmatic reasons for the choice of counting method, and the fourth group on an indicators influence on the research community or how it is influenced by the research community.