The Index itself includes thousands of entries per year. Entries are grouped together under subject headings. Subject headings also include many references to other related subjects where additional entries are located. The unit of analysis for this database is an entry. The sample is derived by coding the first entry on every odd-numbered page of the index.
Entries are generally identifiable because they have a date, section number, and a page number.
Subject headings and other references do not have full citations. The topics variable allows you to track an issue across time as it is treated in the media, in congressional activity and in budgetary activity. There are two complications to the New York Times and its Index that users should keep in mind. First is that occasional format changes have led to different numbers of articles on each page. Second is that the New York Times and its Index have varied in size over the decades.