ARL has released "ARL Statistics 2014–2015 and Updated Trends Graphs Published."
Here's an excerpt:
The Association of Research Libraries (ARL) has released the ARL Statistics 2014–2015 and updated its free series of graphs showing trends in the ARL Statistics data over time. These two publications present information describing the collections, staffing, expenditures, and service activities of the Association’s 124 member libraries in fiscal year 2014–2015. Of these, 114 are university libraries (15 in Canada and 99 in the US); the remaining 10 are public, governmental, and nonprofit research libraries (1 in Canada, 9 in the US).