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Distribution of studies by year of publication.
| Year of Publication | Number of Studies (%) |
|---|---|
| 2017–2021 | 29 (35%) |
| 2021 | 5 (6%) |
| 2020 | 6 (7%) |
| 2019 | 10 (12%) |
| 2018 | 3 (4%) |
| 2017 | 5 (6%) |
| 2012–2016 | 32 (38%) |
| 2016 | 10 (12%) |
| 2015 | 6 (7%) |
| 2014 | 7 (8%) |
| 2013 | 6 (7%) |
| 2012 | 3 (4%) |
| 2007–2011 | 15 (18%) |
| 2011 | 3 (4%) |
| 2010 | 6 (7%) |
| 2009 | 3 (4%) |
| 2008 | 2 (2%) |
| 2007 | 1 (1%) |
| 2002–2006 | 7 (8%) |
| 2005 | 2 (2%) |
| 2004 | 4 (5%) |
| 2003 | 1 (1%) |
| 1995–2001 | 1 (1%) |
| 1996 | 1 (1%) |
