The National Digital Stewardship Alliance report "Web Archiving in the United States: A 2013 Survey," has just been released and is available at http://www.digitalpreservation.gov/ndsa/working_groups/documents/NDSA_USWebArchivingSurvey_2013.pdf.
The survey, conducted by a team of NDSA members, led by the Content Working Group, took place from October through November of 2013, and builds upon a similar survey undertaken by the NDSA in late 2011. The goal of the survey was to better understand the landscape of web archiving activities in the United States by investigating the organizations involved, the history and scope of their web archiving programs, the types of web content being preserved, the tools and services being used, access and discovery services being provided, and overall policies related to web archiving programs.
You can read more about the report on the Signal blog: