FY 2012 data files released online today (July 2, 2014). A report analyzing the data will be published this Fall.
From the Institute of Museum and Library Services (IMLS):
The Institute of Museum and Library Services [has] released data files for the FY 2012 Public Library Survey (PLS), which provides statistics on the status of public libraries in the United States. The data are collected from approximately 9,000 public libraries with approximately 17,000 individual public library outlets in the 50 states, the District of Columbia, and outlying territories.
Data have been collected annually since 1988 and includes information about library visits, circulation, size of collections, public service hours, staff, electronic resources, operating revenues and expenditures and number of service outlets.
Direct to FY 2012 Public Library (Public Use) Survey Data Files and Documentation
Page also includes links to Public Library Survey Data Files back to 1992.