Open source code has fewer defects per thousand lines of code than proprietary software, according to the 2011 Scan Open Source Integrity Report from the U.S. Department of Homeland Security and Coverity. "The line between open source and proprietary software will continue to blur over time as open source is further cemented in the modern software supply chain," says Coverity's Zack Samocha. The 2011 report analyzed more than 37 million lines of open source software code and more than 300 million lines of proprietary software code from a sample of anonymous Coverity users. Coverity says it used a testing platform that was upgraded this year with the ability to find more new and existing types of defects in software code. The report notes that for open source projects, which have an average project size of 832,000 lines of code, the average number of defects per thousand lines of code was .45. For example, Linux 2.6, PHP 5.3, and PostgreSQL 9.1 had defect densities of .62, .20, and .21, respectively. However, the report found that in propriety codebases, which averaged 7.5 million lines of code, the average defect density was .64.