Years

Relevant Studies

Selected Studies

Percentage

2002

4

1

1.8

2003

5

2

3.5

2004

3

2

3.5

2005

11

3

8.9

2006

3

1

1.8

2007

7

4

7.1

2008

6

4

7.1

2009

22

4

7.1

2010

32

7

17.8

2011

14

4

7.1

2012

23

5

8.9

2013

18

6

10.7

2014

14

6

10.7

2015

12

7

17.8

Total

162

56