ProQuest Dissertations and Theses
Content 
The ProQuest Dissertation database provides over 2.4 million records, with 550,000 dissertations and theses in social sciences proposed by US universities and schools; they are indexed, abstracted and retrievable in full-text as pdf format
Selection 
Theses and documents are sent to ProQuest by Universities, schools or authors and then are included in the database according to specific format guidelines
Format
About two million dissertations and theses are available as full-text in pdf format (or tiff images) for subscribers. The other records are indexed, and most of them available only as abstracts
Information density
With so many items, dating back to 1861, provided by over 1,000 universities and schools in the US, this database has several layers of excellent data
Content Pertinence to Political Science
While virtually any scientific field is covered here, about half a million records concern social sciences (i.e. about 65,000 in political science, 110,000 in sociology, 90,000 in economics, etc...)
Updating Rate
The database is updated according to the dissertations' submission by institutions or authors, but overall the content material is quite up to date