Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of a time duration related quesry and we are supposed to write answer to a question that involves event “frequency", which refers to how often an event is likely to be repeated. For example, "taking showers" typically occurs ~5 times a week, "going to saturday market" usually happens every few weeks/months, etc. 
 Note that a lot of the questions could have more than one correct answers. We only need a single most-likely answer. Please try to keep your "answer" as simple as possible. Concise and simple "answer" is preferred over those complex and verbose ones.  

Sentence: More recently, films such as Das Boot (1981), The Never Ending Story (1984) Run Lola Run (1998), Das Experiment (2001), Good Bye Lenin! (2003), Gegen die Wand (Head-on) (2004) and Der Untergang (Downfall) (2004) have enjoyed international success. In 2002 the Academy Award for Best Foreign Language Film went to Caroline Link's Nowhere in Africa, in 2007 to Florian Henckel von Donnersmarck's The Lives of Others. The Berlin International Film Festival, held yearly since 1951, is one of the world's foremost film and cinema festivals. 
Question: How often is the Berlin International Film Festival held?

yearly