Google made several major algorithm updates beginning in 2011 that changed the SEO landscape. The Panda update in February 2011 targeted thin and low-quality content, affecting up to 12% of search results. It rolled out over months. Panda updates continued periodically. Penguin launched in April 2012 and targeted sites participating in link schemes, shaking the SEO world again. Both updates emphasized that high-quality, unique content is important for search rankings. Sites learned they needed relevant content for users rather than thin content or link schemes. Google released several versions of Penguin over subsequent years to address spammy linking practices.