Verizon | 2013 Data breach investigations report (PDF linked from this page)
From ‘Results and analysis’:
“The 2012 combined dataset represents the largest we have ever covered in any single year, spanning 47,000+ reported security incidents, 621 confirmed data disclosures, and at least 44 million compromised records (that we were able to quantify). Over the entire nine-year range of this study, that tally now exceeds 2,500 data disclosures and 1.1 billion compromised records.”
(Source: datasecuritylawjournal.com)